* Introduce Gql-Middleware config as a yml file
* use path /usr/share/bbb-graphql-middleware/ instead of /usr/local/bigbluebutton/bbb-graphql-middleware
* remove /etc/default/bbb-graphql-middleware file
* Refactor gql-middleware channels and remove dedicated channel to establish init connection
* remove unnecessary routin to wait mutations to complete before invalidate Hasura connection