Add endpoint for leaving invited events

src/api/events.py

@@ -320,6 +320,30 @@ async def delete_event(event_id: PydanticObjectId, user: CurrentUserDep) -> Resp
     return Response(status_code=status.HTTP_204_NO_CONTENT)
 
 
+@events_router.delete("/{event_id}/invited")
+async def delete_invited_event(event_id: PydanticObjectId, user: CurrentUserDep) -> Response:
+    """Remove yourself as an attendee of given event."""
+    event = await Event.get(event_id, fetch_links=True)
+    if event is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Event with given id doesn't exist")
+
+    for attendee in event.attendees:
+        if cast(User, attendee).id == user.id:
+            break
+    else:  # nobreak
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="You can only access events you attend",
+        )
+
+    event.attendees.remove(attendee)
+    _ = await event.replace()
+
+    # NOTE: We might want to notify the event owner about the attendee leaving
+
+    return Response(status_code=status.HTTP_204_NO_CONTENT)
+
+
 @events_router.post("")
 async def create_event(
     user: CurrentUserDep,