chore(config_flow): use DOMAIN constant + clear pending cred after commit

Two small cleanups in async_oauth_create_entry / _commit_pending_credential:

- Replace the two remaining "u_tec" string literals with the DOMAIN
  constant for consistency with the rest of the file (and with
  async_migrate_entry, which already uses DOMAIN throughout).

- Clear self._pending_credential after the successful commit. Not a
  bug today (the flow doesn't loop back), but prevents a footgun if
  anyone later adds a retry path that would re-commit the same cred.

Author: geofffranks

custom_components/u_tec/config_flow.py

@@ -186,7 +186,8 @@ async def async_oauth_create_entry(
         """
         if self._pending_credential is not None:
             await self._commit_pending_credential()
-            data = {**data, "auth_implementation": "u_tec"}
+            self._pending_credential = None
+            data = {**data, "auth_implementation": DOMAIN}
 
         if self.source == SOURCE_RECONFIGURE:
             entry = self._get_reconfigure_entry()
@@ -267,7 +268,7 @@ async def _commit_pending_credential(self) -> None:
             self.hass,
             DOMAIN,
             self._pending_credential,
-            "u_tec",
+            DOMAIN,
         )
 
         if storage is not None: