MSC3909: Membership based mutes

[FSG-Cat]

Rendered

MSC Co Authored by @FSG-Cat and @Gnuxie

Signed-off-by: Catalan Lover [email protected]

[luxaritas]

I wonder if there's another way to approach this that would allow users to rejoin as muted (which I would want to allow from a policy perspective with how I use mutes, personally - eg imagine if #55 is implemented and I do an IP mute space-wide of a classroom because of misbehavior but still want them to see activity). What would be the tradeoffs of a separate leave-mute membership type, or separate state to indicate mute status? I guess the latter feels a bit in the direction of RBAC, though from a semantic point of view the line between "permission" and "membership status" is a bit fuzzy.