Add pub/sub content-type info (#1158)

* add pub/sub content-type info

* datacontenttype clarification

* Update pubsub_api.md

* add custom cloudevent info

* reorder

* Update howto-publish-subscribe.md

* Update howto-publish-subscribe.md

Co-authored-by: Mark Fussell <mfussell@microsoft.com>

daprdocs/content/en/developing-applications/building-blocks/pubsub/howto-publish-subscribe.md

@@ -14,6 +14,12 @@ Using Pub/Sub, you can enable scenarios where event consumers are decoupled from
 Dapr provides an extensible Pub/Sub system with At-Least-Once guarantees, allowing developers to publish and subscribe to topics.
 Dapr provides components for pub/sub, that enable operators to use their preferred infrastructure, for example Redis Streams, Kafka, etc.
 
+## Content Types
+
+When publishing a message, it's important to specify the content type of the data being sent.
+Unless specified, Dapr will assume `text/plain`. When using Dapr's HTTP API, the content type can be set in a `Content-Type` header.
+gRPC clients and SDKs have a dedicated content type parameter.
+
 ## Step 1: Setup the Pub/Sub component
 The following example creates applications to publish and subscribe to a topic called `deathStarStatus`.
 
@@ -379,6 +385,14 @@ app.listen(process.env.PORT || port, () => console.log(`Listening on port ${port
 ```
 {{% /codetab %}}
 {{< /tabs >}}
+
+## Sending a custom CloudEvent
+
+Dapr automatically takes the data sent on the publish request and wraps it in a CloudEvent 1.0 envelope.
+If you want to use your own custom CloudEvent, make sure to specify the content type as `application/cloudevents+json`.
+
+See info about content types [here](#Content-Types).
+
 ## Next steps
 
 - Try the [Pub/Sub quickstart sample](https://github.com/dapr/quickstarts/tree/master/pub-sub)
@@ -386,4 +400,4 @@ app.listen(process.env.PORT || port, () => console.log(`Listening on port ${port
 - Learn about [message time-to-live]({{< ref pubsub-message-ttl.md >}})
 - Learn [how to configure Pub/Sub components with multiple namespaces]({{< ref pubsub-namespaces.md >}})
 - List of [pub/sub components]({{< ref setup-pubsub >}})
-- Read the [API reference]({{< ref pubsub_api.md >}})
+- Read the [API reference]({{< ref pubsub_api.md >}})

daprdocs/content/en/reference/api/pubsub_api.md

@@ -45,6 +45,14 @@ curl -X POST http://localhost:3500/v1.0/publish/pubsubName/deathStarStatus \
      }'
 ```
 
+### Headers
+
+The `Content-Type` header tells Dapr which content type your data adheres to when constructing a CloudEvent envelope.
+The value of the `Content-Type` header populates the `datacontenttype` field in the CloudEvent.
+Unless specified, Dapr assumes `text/plain`. If your content type is JSON, use a `Content-Type` header with the value of `application/json`.
+
+If you want to send your own custom CloundEvent, use the `application/cloudevents+json` value for the `Content-Type` header.
+
 #### Metadata
 
 Metadata can be sent via query parameters in the request's URL. It must be prefixed with `metadata.` as shown below.
@@ -143,7 +151,7 @@ other | warning is logged and message to be retried
 
 ## Message envelope
 
-Dapr Pub/Sub adheres to version 1.0 of Cloud Events.
+Dapr Pub/Sub adheres to version 1.0 of CloudEvents.
 
 ## Related links