Incorporate RLS into the quickstart

[joshua-spacetime]

Most people will want to see that access to chat messages can be restricted and how to do it.

[gefjon]

I think that probably this should be a follow-up tutorial, not included within the quickstart itself. Similar to how currently the module and client tutorials are separate documents. I am unsure how exactly to extend the quickstart-chat module to allow meaningful RLS rules, but I bet we can figure something out. Maybe separate channels, or DMs?