M8-R01: add configurable MQTT client identity

app/integrations/mqtt.py

@@ -48,6 +48,7 @@ MQTT_SETTINGS_KEYS = {
     "mqtt_username",
     "mqtt_password",
     "mqtt_tls_enabled",
+    "mqtt_client_id",
 }
 
 
@@ -65,6 +66,16 @@ def _is_configured(settings: Settings) -> bool:
     return bool(settings.mqtt_enabled and settings.mqtt_broker_host)
 
 
+def mqtt_source_client_id(base_client_id: str, source_id: int) -> str:
+    """Return a stable, deployment-scoped identity for one DSMR source."""
+    return f"{base_client_id}-dsmr-source-{source_id}"
+
+
+def mqtt_test_client_id(base_client_id: str) -> str:
+    """Return a transient test identity that cannot evict a long-lived client."""
+    return f"{base_client_id}-test"
+
+
 class MqttManager:
     """Long-lived MQTT client wrapper.
 
@@ -236,6 +247,7 @@ class MqttManager:
         password: str,
         tls_enabled: bool,
         subscriptions: dict[str, Callable[[bytes], None]],
+        base_client_id: str = "home-automation",
     ) -> bool:
         """Replace one source-owned client and its handlers.
 
@@ -253,7 +265,7 @@ class MqttManager:
             captured_subscriptions = dict(subscriptions)
             client = mqtt.Client(
                 callback_api_version=mqtt.CallbackAPIVersion.VERSION2,
-                client_id=f"home-automation-dsmr-{source_id}",
+                client_id=mqtt_source_client_id(base_client_id, source_id),
             )
 
             def _on_connect(
@@ -360,7 +372,7 @@ class MqttManager:
         """Build a fresh paho Client, configure it, and call loop_start + connect."""
         client = mqtt.Client(
             callback_api_version=mqtt.CallbackAPIVersion.VERSION2,
-            client_id="home-automation",
+            client_id=settings.mqtt_client_id,
         )
 
         # Callbacks — VERSION2 on_connect signature: