Learn unknown device MQTT credentials on first connect

[piotrkochan]

My Saros 10R ignores bootstrap credentials from nc_prepare (don't know why...) and connects to MQTT using its own device credentials. The server rejects the connection because device_mqtt_usr is empty, and there's no way to identify it- record_mqtt_topic only runs after authentication succeeds.

This PR adds a fallback. When authentication returns unknown_device_mqtt_username, if exactly one device has an empty mqtt_usr and a non-empty did, it assigns the credentials from the CONNECT packet. It does nothing if there are 0 or 2 or more candidates.

I'm not sure this is the right approach, but it did unblock my setup.

Relates to #19.

[jdejaegh]

Thanks for the PR, it did unblock my vacuum as well! I use a Roborock S7 (roborock.vacuum.a15) and it was stuck on connecting to the Wi-Fi and your patch helped it connect to MQTT.

However, my phone would not connect to the MQTT server with the same error after installing the patched application on Android. I ended up adding the following code to just allow all MQTT credentials (I won't create a PR as this is hacky)

@@ -232,6 +233,12 @@ class MqttTlsProxy:
                 if learned_device is not None:
                     return True, "device_mqtt_learned", info
 
+            learned_device = self.runtime_credentials.learn_device_mqtt_credentials(
+                username=username,
+                password=password,
+            )
+            return True, "device_mqtt_learned", info
+
         return False, "invalid_mqtt_credentials", info
 
     @classmethod

[Lash-L]

Hey @piotrkochan thank you for the PR. I ended up taking a different approach. Thank you so much for working through your issue and sharing a solution though!