Add option for groups to hide their membership list from the world

[turt2live]

This is intended to be used by bridges, but may have usefulness for other communities. The idea behind this is that members can have flair in designated rooms, but not be visible as a group member otherwise. Bridges may be interested in this for their portal rooms where the bridged users have flair, but the group they are part of doesn't supply an easily acquirable list of users to spam.

Solves element-hq/element-web#5365 (which probably shouldn't have been a Riot ticket in the first place).

[matrixbot]

Can one of the admins verify this patch?

[matrixbot]

Can one of the admins verify this patch?

[matrixbot]

Can one of the admins verify this patch?

[erikjohnston]

Erik
Yay
TravisR: RE #2563: would it be enough for users joining the group to ask that they aren't displayed in the user list?
(Which I think is a thing we already do)
s/do/theoretically support/
oh good, flake8 have released a new version with new warnings

TravisR
Erik: would that be the is_public flag that's not exposed? The goal is flair without appearing in the membership list.

Erik
sort of
So flair is based off of whether you publicise your membership of a group on your profile (assuming for a second that user profiles are a thing)
which is orthogonal to whether you publicise your membership of a group on the group profile
Now, the is_public flag in the group read APIs indicates whether that user is shown to people not in the group. However, the settings in reality can be a lot more granular than just public/private toggle, e.g. a group server may support privacy settings where only a subset of users can see other subsets
So to set the public/private settings is more complicated than just an is_public flag
i.e. we already do what you want on a per user granularity (assuming it works)
TravisR: ^

TravisR
Yea, for my case I'm not too concerned about members of the group seeing each other (as they're all bridge users). Just don't want a spam list :p

Erik
yeah, fair :)
Now, none pf the privacy settings are tested at all atm
nor used, so I'm not sure how much I want to commit to them working...
(or hte API not changing)

TravisR
I'll do the necessary database updates and find out I guess. If it works, I'll track changes to groups to avoid blowing up the server
Feel free to close the pr. I'm not near a desktop atm