Adding user notifications panel
This is a huge change introduced to how the server works, as we are switching to using websockets (for live notifications!) in addition to regular HTTP requests. The API stays roughly the same (with the addition of more precise types), but the underlying server switches from WSGI to ASGI.
This also means the user will benefit from feedback from the notification API upon actions that are asynchronous (i.e. someone else sending them a message, or some background process finishing).