add binding concepts and specs (#14)

* add binding concepts and specs

* Performed edits on the doc

We need to be clear between saying binding are used to trigger events from external systems or external resources and then stick with this. Hence getting the terminology section written soon, would be best.

concepts/bindings/bindings.md

@@ -1,3 +1,57 @@
-# documentation 
+# Bindings
 
-Content for this file to be added
+Using bindings, you can trigger your app with events coming in from external systems, or invoke external systems.
+Bindings allow for on-demand, event-driven compute scenarios, and dapr bindings help developers with the following:
+
+* Remove the complexities of connecting to, and polling from, messaging systems such as queues, message buses etc
+* Focus on business logic and not the implementation details of how interact with a system.
+* Keep the code free from SDKs or libraries
+* Handles retries and failure recovery
+* Switch between bindings at runtime time
+* Enable portable applications where environment-specific bindings are set-up and no code changes are required
+
+Bindings are developed independently of dapr runtime. You can view and contribute to the bindings [here](https://github.com/actionscore/components-contrib/tree/master/bindings). 
+
+## Supported Bindings and Specs
+
+Every binding has its own unique set of properties. Click the name link to see the component YAML for each binding.
+
+| Name  | Input Binding | Output Binding | Status
+| ------------- | -------------- | -------------  | ------------- |
+| [Kafka](./specs/kafka.md) | V | V | Experimental |
+| [RabbitMQ](./specs/rabbitmq.md) | V  | V | Experimental |
+| [AWS SQS](./specs/sqs.md) | V | V | Experimental |
+| [AWS SNS](./specs/sns.md) |  | V | Experimental |
+| [Azure EventHubs](./specs/eventhubs.md) | V | V | Experimental |
+| [Azure CosmosDB](./specs/cosmosdb.md) |  V | | Experimental |
+| [GCP Storage Bucket](./specs/gcpbucket.md)  | | V | Experimental |
+| [HTTP](./specs/http.md) |  | V | Experimental |
+| [MQTT](./specs/mqtt.md) | V | V | Experimental |
+| [Redis](./specs/redis.md) |  | V | Experimental |
+| [AWS DynamoDB](./specs/dynamodb.md) | | V | Experimental |
+| [AWS S3](./specs/s3.md) | | V | Experimental |
+| [Azure Blob Storage](./specs/blobstorage.md) | | V | Experimental |
+
+## Input Bindings
+
+Input bindings are used to trigger your app when an event from an external system has occured.
+An optional payload and metadata might be sent with the request.
+
+In order to receive events from an input binding:
+
+1. Define the component YAML that describes the type of bindings and its metadata (connection info, etc.)
+2. Listen on an HTTP endpoint for the incoming event, or use the gRPC proto library to get incoming events.
+
+Read the [How To](../../howto) section to get started with input bindings.
+
+## Output Bindings
+
+Output bindings allow users to invoke external systems
+An optional payload and metadata can be sent with the invocation request.
+
+In order to invoke an output binding:
+
+1. Define the component YAML that describes the type of bindings and its metadata (connection info, etc.)
+2. Use the HTTP endpoint or gRPC method to invoke the binding with an optional payload
+
+ Read the [How To](../../howto) section to get started with output bindings.

concepts/bindings/specs/blobstorage.md

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+# Azure Blob Storage Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.azure.blobstorage
+  metadata:
+  - name: storageAccount
+    value: https://******.documents.azure.com:443/
+  - name: storageAccessKey
+    value: ***********
+  - name: container
+    value: container1
+```
+
+`storageAccount` is the Blob Storage account name.
+`storageAccessKey` is the Blob Storage access key.
+`container` is the name of the Blob Storage container to write to.

concepts/bindings/specs/cosmosdb.md

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+# Azure CosmosDB Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.azure.cosmosdb
+  metadata:
+  - name: url
+    value: https://******.documents.azure.com:443/
+  - name: masterKey
+    value: *****
+  - name: database
+    value: db
+  - name: collection
+    value: collection
+  - name: partitionKey
+    value: message
+```
+
+`url` is the CosmosDB url.
+`masterKey` is the CosmosDB account master key.
+`database` is the name of the CosmosDB database.
+`collection` is name of the collection inside the database.
+`partitionKey` is the name of the partitionKey to extract from the payload.

concepts/bindings/specs/dynamodb.md

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+# AWS DynamoDB Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.aws.dynamodb
+  metadata:
+  - name: region
+    value: us-west-2
+  - name: accessKey
+    value: *****************
+  - name: secretKey
+    value: *****************
+  - name: table
+    value: items
+```
+
+`region` is the AWS region.
+`accessKey` is the AWS access key.
+`secretKey` is the AWS secret key.
+`table` is the DynamoDB table name.

concepts/bindings/specs/eventhubs.md

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+# Azure EventHubs Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.azure.eventhubs
+  metadata:
+  - name: connectionString
+    value: https://<address>
+  - name: consumerGroup  # Optional
+    value: group1
+  - name: messageAge
+    value: 5s         # Optional. Golang duration
+```
+
+`connectionString` is the EventHubs connection string.
+`consumerGroup` is the name of an EventHubs consumerGroup to listen on.
+`messageAge` allows to receive messages that are not older than the specified age.

concepts/bindings/specs/gcpbucket.md

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+# GCP Storage Bucket Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.gcp.storage
+  metadata:
+  - name: bucket
+    value: mybucket
+  - name: type
+    value: service_account
+  - name: project_id
+    value: project_111
+  - name: private_key_id
+    value: *************
+  - name: client_email
+    value: name@domain.com
+  - name: client_id
+    value: '1111111111111111'
+  - name: auth_uri
+    value: https://accounts.google.com/o/oauth2/auth
+  - name: token_uri
+    value: https://oauth2.googleapis.com/token
+  - name: auth_provider_x509_cert_url
+    value: https://www.googleapis.com/oauth2/v1/certs
+  - name: client_x509_cert_url
+    value: https://www.googleapis.com/robot/v1/metadata/x509/<project-name>.iam.gserviceaccount.com
+  - name: private_key
+    value: PRIVATE KEY
+```
+
+`bucket` is the bucket name.
+`type` is the GCP credentials type.
+`project_id` is the GCP project id.
+`private_key_id` is the GCP private key id.
+`client_email` is the GCP client email.
+`client_id` is the GCP client id.
+`auth_uri` is Google account oauth endpoint.
+`token_uri` is Google account token uri.
+`auth_provider_x509_cert_url` is the GCP credentials cert url.
+`client_x509_cert_url` is the GCP credentials project x509 cert url.
+`private_key` is the GCP credentials private key.

concepts/bindings/specs/http.md

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+# HTTP Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.http
+  metadata:
+  - name: url
+    value: http://something.com
+  - name: method
+    value: GET
+```
+
+`url` is the HTTP url to invoke.
+`method` is the HTTP verb to use for the request.

concepts/bindings/specs/kafka.md

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+# Kafka Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.kafka
+  metadata:
+  - name: topics # Optional. in use for input bindings
+    value: topic1,topic2
+  - name: brokers
+    value: localhost:9092,localhost:9093
+  - name: consumerGroup
+    value: group1
+  - name: publishTopic # Optional. in use for output bindings
+    value: topic3
+```
+
+`topics` is a comma separated string of topics for an input binding.
+`brokers` is a comma separated string of kafka brokers.
+`consumerGroup` is a kafka consumer group to listen on.
+`publishTopic` is the topic to publish for an output binding.

concepts/bindings/specs/mqtt.md

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+# MQTT Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.mqtt
+  metadata:
+  - name: url
+    value: mqtt[s]://[username][:password]@host.domain[:port]
+  - name: topic
+    value: topic1
+```
+
+`url` is the MQTT broker url.
+`topic` is the topic to listen on or send events to.

concepts/bindings/specs/rabbitmq.md

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+# RabbitMQ Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.rabbitmq
+  metadata:
+  - name: queueName
+    value: queue1
+  - name: host
+    value: amqp://guest:guest@localhost:5672
+  - name: durable
+    value: true
+  - name: deleteWhenUnused
+    value: false
+```
+
+`queueName` is the RabbitMQ queue name.
+`host` is the RabbitMQ host address.
+`durable` tells RabbitMQ to persist message in storage.
+`deleteWhenUnused` enables or disables auto-delete.

concepts/bindings/specs/redis.md

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+# Redis Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.redis
+  metadata:
+  - name: redisHost
+    value: <address>:6379
+  - name: redisPassword
+    value: **************
+```
+
+`redisHost` is the Redis host address.
+`redisPassword` is the Redis password.

concepts/bindings/specs/s3.md

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+# AWS S3 Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.aws.s3
+  metadata:
+  - name: region
+    value: us-west-2
+  - name: accessKey
+    value: *****************
+  - name: secretKey
+    value: *****************
+  - name: bucket
+    value: mybucket
+```
+
+`region` is the AWS region.
+`accessKey` is the AWS access key.
+`secretKey` is the AWS secret key.
+`table` is the name of the S3 bucket to write to.

concepts/bindings/specs/sns.md

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+# AWS SNS Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.aws.sns
+  metadata:
+  - name: region
+    value: us-west-2
+  - name: accessKey
+    value: *****************
+  - name: secretKey
+    value: *****************
+  - name: topicArn
+    value: mytopic
+```
+
+`region` is the AWS region.
+`accessKey` is the AWS access key.
+`secretKey` is the AWS secret key.
+`topicArn` is the SNS topic name.

concepts/bindings/specs/sqs.md

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+# AWS SQS Binding Spec
+
+```
+apiVersion: actions.io/v1alpha1
+kind: Component
+metadata:
+  name: <name>
+spec:
+  type: bindings.aws.sqs
+  metadata:
+  - name: region
+    value: us-west-2
+  - name: accessKey
+    value: *****************
+  - name: secretKey
+    value: *****************
+  - name: queueName
+    value: items
+```
+
+`region` is the AWS region.
+`accessKey` is the AWS access key.
+`secretKey` is the AWS secret key.
+`queueName` is the SQS queue name.