External nats streaming (#1576)

Support for external NATS streaming instead of the one deployed with Fission

Co-authored-by: Shaun Cutts <shaunc@factfiber.com>

charts/fission-all/values.yaml

@@ -29,6 +29,7 @@ controllerPort: 31313
 routerPort: 31314
 
 ## Port at which NATS streaming service should be exposed
+## (only if nats enabled and not external)
 natsStreamingPort: 31316
 
 ## Set to false if you create the namespaces manually
@@ -142,10 +143,28 @@ router:
 ## Message queue trigger config
 ### NATS Streaming, enabled by default
 nats:
+  # whether or not to use NATS
   enabled: true
+
+  # if true, don't install NATS, but
+  external: false
+
+  # Address of NATS server (domain:port)
+  # change from default for external NATS
+  hostaddress: 'nats-streaming:4222'
+
+  # Authorization token to use with NATS
   authToken: "defaultFissionAuthToken"
+
+  # NATS streaming clusterID
   clusterID: "fissionMQTrigger"
 
+  # Client name registered with NATS streaming 
+  clientID: "fission"
+
+  # Queue group registered with NATS streaming 
+  queueGroup: "fission-messageQueueNatsTrigger"
+
 ## Azure-storage-queue: enable and configure the details
 azureStorageQueue:
   enabled: false