Add unique-ids to maxcube component (#49196)

homeassistant/components/maxcube/climate.py

@@ -87,6 +87,11 @@ class MaxCubeClimate(ClimateEntity):
         """Return the name of the climate device."""
         return self._name
 
+    @property
+    def unique_id(self):
+        """Return a unique ID."""
+        return self._device.serial
+
     @property
     def min_temp(self):
         """Return the minimum temperature."""