Add MQTT asyncapi definition for Agent Service

This commit adds the MQTT asyncapi definition for the Agent Service. It includes the necessary channels and messages for remote command execution, remote terminal, heartbeat service, and other functionalities. The asyncapi version is set to 2.6.0, and the Agent Service version is 0.13. The description provides an overview of the Agent Service's capabilities. The example payload is included, demonstrating the usage of SenML for different commands.

Signed-off-by: SammyOina <sammyoina@gmail.com>

api/asynapi/mqtt.yaml

@@ -0,0 +1,21 @@
+asyncapi: 2.6.0
+info:
+  title: Agent Service
+  version: 0.13
+  description: Agent service provides remote command execution, remote terminal, heartbeat service for services on edge and edgex SMA.
+channels:
+  channels/{channel_id}/messages/req:
+    publish:
+      message:
+        $ref: '#/componenets/messages/agentMessage'
+components:
+  messages:
+    agentMessage:
+      payload:
+        type: object
+        example: |
+        ### SenML
+        ```json
+        [{"bn":"1:", "n":"<command>", "vs":"<content>"}]
+        ```
+        #### Commands: exec, control, config, service, term