`RoomTakedownProtection` should give some info about who joined the room

[Gnuxie]

Today, for the first time, I received a RoomTakedownProtection notification from Draupnir. I can see the room name, the ID, and the creator, but there is no indication anywhere as to which user has currently interacted with the room.

yeah, that information technically is available but providing it in ui is difficult in order to not lead people to wrong conclusions (and we'd also have to snapshot it and store it)

also while we're thinking here, we probably want to know when a user tried to join a blocked room too from the homeserver

Context: https://matrix.to/#/!IaWNErZAgQUhGqJXjX:matrix.org/%24efBYHmvpBG6QBbkYJ3v9TWBw0Wxn26dPinEDc3vN8AU?via=matrix.org&via=breadpirates.chat&via=unredacted.org
Reported by: @Tealk:rollenspiel.chat