feat(TaskProcessing): Add trigger_handler to set_handlers() (#382)

See nextcloud/app_api#683 for the corresponding
AppAPI PR.

Changes proposed in this pull request:

* Add a `trigger_handler` param to set_handlers() that will be called
when the /trigger endpoint is requested by AppAPI.

---------

Signed-off-by: Marcel Klehr <mklehr@gmx.net>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: marcelklehr

nc_py_api/ex_app/integration_fastapi.py

@@ -61,6 +61,7 @@ def set_handlers(
     default_init: bool = True,
     models_to_fetch: dict[str, dict] | None = None,
     map_app_static: bool = True,
+    trigger_handler: typing.Callable[[str], typing.Awaitable[None] | None] | None = None,
 ):
     """Defines handlers for the application.
 
@@ -93,6 +94,8 @@ def set_handlers(
     :param map_app_static: Should be folders ``js``, ``css``, ``l10n``, ``img`` automatically mounted in FastAPI or not.
 
         .. note:: First, presence of these directories in the current working dir is checked, then one directory higher.
+
+    :param trigger_handler: callback that is called for task processing `trigger` events with the id of the provider.
     """
     if models_to_fetch is not None and default_init is False:
         raise ValueError("`models_to_fetch` can be defined only with `default_init`=True.")
@@ -125,6 +128,21 @@ async def init_callback(b_tasks: BackgroundTasks, nc: typing.Annotated[Nextcloud
     if map_app_static:
         __map_app_static_folders(fast_api_app)
 
+    if trigger_handler:
+        if asyncio.iscoroutinefunction(trigger_handler):
+
+            @fast_api_app.post("/trigger")
+            async def trigger_callback(providerId: str):  # pylint: disable=invalid-name
+                await trigger_handler(providerId)
+                return JSONResponse(content={})
+
+        else:
+
+            @fast_api_app.post("/trigger")
+            def trigger_callback(providerId: str):  # pylint: disable=invalid-name
+                trigger_handler(providerId)
+                return JSONResponse(content={})
+
 
 def __map_app_static_folders(fast_api_app: FastAPI):
     """Function to mount all necessary static folders to FastAPI."""