Support simultaneous open connections in LiveServerTestCase
|Patch needs improvement:
django-websockets-redis is a popular library to use websockets and Django. However the LiveServerTestCase does not work with it because it is single threaded.
Currently it is not possible to simulate more than one client at a time. Django’s built in LiveServerTestCase can not handle more than one simultaneous open connection, and thus more sophisticated tests with more than one active Websockets are not possible.
We should make that possible and handle simultaneous open connections