Notify channel operation and setting change

[BECATRUE]

Feature you want to implement

To notify channels operation status and synchronize channels setting, the server should offer the feature notifying them whenever changed.

How the feature is implemented

It will be implemented using WebSocket. Django offers Channels for WebSocket, hence I decided to utilize this.

1. Update asgi.py to run the server with asynchronous server gateway interface.
2. Implement two Consumers to notify channels operation status and setting. The group of each Django channel is set to its target WLM channel.
3. In the request handler to update operation or setting model, send the change to the corresponding group using group_send().

Additional context

You can refer to the followings for how to use Channels.

• https://channels.readthedocs.io/en/latest/index.html (If you aren't similar to Channels, I strongly recommend to read the tutorial.)
• https://velog.io/@mimijae/Django-Django-rest-framework%EB%A1%9C-%EC%9B%B9%EC%86%8C%EC%BC%93-%EC%B1%84%ED%8C%85-%EC%84%9C%EB%B2%84-%EA%B5%AC%ED%98%84%ED%95%98%EA%B8%B01