See room version before I join a room

[aaronraimist]

Is your suggestion related to a problem? Please describe.
I never want to join a v1 room again so I don't have to deal with possibly being stuck in it forever.

Describe the solution you'd like
I would like a way to see what the room version is for a room I am being invited to or am considering joining. This should be off by default or even just a labs flag, most people should not need to know what room versions are.

Describe alternatives you've considered

• An option in Synapse to never allow me to join specific room versions. This is probably not a good solution for many people yet, even I might want to make one or two exceptions to this rule.
• An option in Riot that warns me when I try to join a v1 room, maybe this is a better solution then just showing me what version it is.

[turt2live]

one possible implementation of this is to have some red text saying "This room version is unstable and may not work properly. Are you sure you want to join?"

at least for the day that we finally flag v1 and company as unstable.