Mobile App: Register devices into the registry (#21856)

* Register devices into the registry

* Switch to device ID instead of webhook ID

* Rearchitect mobile_app to support config entries

* Kill DATA_REGISTRATIONS by migrating registrations into config entries

* Fix tests

* Improve how we get the config_entry_id

* Remove single_instance_allowed

* Simplify setup_registration

* Move webhook registering functions into __init__.py since they are only ever used once

* Kill get_registration websocket command

* Support description_placeholders in async_abort

* Add link to mobile_app implementing apps in abort dialog

* Store config entry and device registry entry in hass.data instead of looking it up

* Add testing to ensure that the config entry is created at registration

* Fix busted async_abort test

* Remove unnecessary check for entry is None

homeassistant/data_entry_flow.py

@@ -170,11 +170,13 @@ class FlowHandler:
         }
 
     @callback
-    def async_abort(self, *, reason: str) -> Dict:
+    def async_abort(self, *, reason: str,
+                    description_placeholders: Optional[Dict] = None) -> Dict:
         """Abort the config flow."""
         return {
             'type': RESULT_TYPE_ABORT,
             'flow_id': self.flow_id,
             'handler': self.handler,
-            'reason': reason
+            'reason': reason,
+            'description_placeholders': description_placeholders,
         }