GraphQL subscriptions

Graphene lib doesn`t support subscriptions, but there are libs that implements subscriptions using web sockets.
[Description](https://docs.graphene-python.org/projects/django/en/latest/subscriptions/)

Read the issue and its linked Graphene-Django subscriptions description first, then inspect the repository to identify the current GraphQL entry points and how a subscription library could fit. Done means the project has a defined, working subscription integration over WebSockets, with its supported usage and validation documented.

由索引模型根据 Issue 内容生成。