feat: add suback packet to subscribe callback (#1923)

* Subscribe callback to also include the suback

* Lint

* Update existing subscribe completion test with a suback check

---------

Co-authored-by: Daniel Lando <daniel.sorridi@gmail.com>
Co-authored-by: Bret Ambrose <bambrose@amazon.com>

src/lib/client.ts

@@ -383,6 +383,7 @@ export type OnDisconnectCallback = (packet: IDisconnectPacket) => void
 export type ClientSubscribeCallback = (
 	err: Error | null,
 	granted?: ISubscriptionGrant[],
+	packet?: ISubackPacket,
 ) => void
 export type OnMessageCallback = (
 	topic: string,
@@ -1248,7 +1249,7 @@ export default class MqttClient extends TypedEventEmitter<MqttClientEventCallbac
 						}
 					}
 
-					callback(err, subs)
+					callback(err, subs, packet2)
 				},
 			}
 			this.log('subscribe :: call _sendPacket')

test/abstract_client.ts

@@ -2501,7 +2501,7 @@ export default function abstractTest(server, config, ports) {
 			const topic = 'test'
 
 			client.once('connect', () => {
-				client.subscribe(topic, { qos: 2 }, (err, granted) => {
+				client.subscribe(topic, { qos: 2 }, (err, granted, suback) => {
 					if (err) {
 						done(err)
 					} else {
@@ -2517,6 +2517,8 @@ export default function abstractTest(server, config, ports) {
 							expectedResult.properties = undefined
 						}
 						assert.include(granted[0], expectedResult)
+						assert.exists(suback, 'suback not given')
+						assert.deepStrictEqual(suback.granted, [2])
 						client.end((err2) => done(err2))
 					}
 				})