Tell people the server is temporary during testing

[kewisch]

Enhancement Proposal

We need some way to tell people joining that the server state is temporary and we're in testing. Potentially leverage https://github.com/matrix-org/synapse/blob/develop/docs/consent_tracking.md

[kewisch]

It appears there is no way to do this other than setting a topic or having a bot greet people.

[amandahla]

Closing this issue since no longer apply, thanks for the input!