Documentation for MQTT topics with path parameters (aklivity#311)

Author: epieffe

src/reference/config/bindings/mqtt/.partials/routes.md

@@ -52,26 +52,56 @@ An MQTT client identifier, allowing the usage of wildcards.
 
 > `array` of `object`
 
-Array of MQTT topic names for publish capability.
+Array of MQTT topic configs for publish capability.
 
 #### publish[].topic
 
 > `string`
 
 The MQTT topic to match on that supports standard MQTT wildcards `/+/`, `/#`.
 
+Also, supports embedded parameters (e.g., `{id}`) for dynamic topic matching.
+
+#### publish[].params
+
+> `object` as map of named `string`
+
+Enforce validation of topic embedded parameters.
+
+```yaml
+publish:
+  - topic: device/{id}
+    params:
+      id: ${guarded['jwt'].identity}
+```
+
 #### when[].subscribe
 
 > `array` of `object`
 
-Array of MQTT topic names for subscribe capability.
+Array of MQTT topic configs for subscribe capability.
 
 #### subscribe[].topic
 
 > `string`
 
 The MQTT topic to match on that supports standard MQTT wildcards `/+/`, `/#`.
 
+Also, supports embedded parameters (e.g., `{id}`) for dynamic topic matching.
+
+#### subscribe[].params
+
+> `object` as map of named `string`
+
+Enforce validation of topic embedded parameters.
+
+```yaml
+subscribe:
+  - topic: device/{id}
+    params:
+      id: ${guarded['jwt'].identity}
+```
+
 #### routes[].exit
 
 > `string`

src/reference/config/bindings/mqtt/.partials/server.yaml

@@ -11,12 +11,19 @@
         - v5
         - v3.1.1
     routes:
-      - when:
+      - guarded:
+          my_jwt_guard:
+            - mqtt:stream
+        when:
           - session:
               - client-id: "*"
           - publish:
-              - topic: command/one
-              - topic: command/two
+              - topic: device/{id}/location
+                params:
+                  id: ${guarded['my_jwt_guard'].identity}
+              - topic: device/{id}/temperature
+                params:
+                  id: ${guarded['my_jwt_guard'].identity}
           - subscribe:
               - topic: reply
     exit: mqtt_kafka_proxy