Merge pull request #1117 from kzmake/support-priority-queue-for-rabbitmq-bindings

Add documentation to rabbitmq bindings for Priority Queue

daprdocs/content/en/operations/components/setup-bindings/supported-bindings/rabbitmq.md

@@ -31,6 +31,8 @@ spec:
     value: 0
   - name: exclusive
     value: false
+  - name: maxPriority
+    value: 5
 ```
 
 - `queueName` is the RabbitMQ queue name.
@@ -40,6 +42,7 @@ spec:
 - `ttlInSeconds` is an optional parameter to set the [default message time to live at RabbitMQ queue level](https://www.rabbitmq.com/ttl.html). If this parameter is omitted, messages won't expire, continuing to exist on the queue until processed.
 - `prefetchCount` is an optional parameter to set the [Channel Prefetch Setting (QoS)](https://www.rabbitmq.com/confirms.html#channel-qos-prefetch). If this parameter is omiited, QoS would set value to 0 as no limit.
 - `exclusive` determines whether the topic will be an exclusive topic or not
+- `maxPriority` is an optional parameter to set the [priority queue](https://www.rabbitmq.com/priority.html). If this parameter is omitted, queue will be created as a general queue instead of a priority queue.
 
 {{% alert title="Warning" color="warning" %}}
 The above example uses secrets as plain strings. It is recommended to use a secret store for the secrets as described [here]({{< ref component-secrets.md >}}).
@@ -69,6 +72,30 @@ curl -X POST http://localhost:3500/v1.0/bindings/myRabbitMQ \
       }'
 ```
 
+## Specifying a priority on message level
+
+Priority can be defined at the message level. If `maxPriority` parameter is set, high priority messages will have priority over other low priority messages. 
+
+To set priority at message level use the `metadata` section in the request body during the binding invocation.
+
+The field name is `priority`.
+
+Example:
+
+```shell
+curl -X POST http://localhost:3500/v1.0/bindings/myRabbitMQ \
+  -H "Content-Type: application/json" \
+  -d '{
+        "data": {
+          "message": "Hi"
+        },
+        "metadata": {
+          "priority": "5"
+        },
+        "operation": "create"
+      }'
+```
+
 ## Output Binding Supported Operations
 
 * create