(Bug) room server - allow.read.only should not allow an empty "guest" password

[n2aws]

If you enable "allow.read.only" on a room server right now, you can set a blank guest password.

In that scenario, a user who doesn't type in a password (who should normally be read-only) is granted read/write access.

When allow.read.only is enabled, it should force a non-blank guest password, thus enabling "blank password" users to be read-only, instead of read/write

[github-actions]

This issue is stale because it has been open for 60 days with no activity. Remove the stale label or add a comment if this issue is still relevant, otherwise this issue will automatically close in 7 days.

[axhoff]

Opened #2995 with a focused fix and authorization-matrix regression tests. A blank configured guest password now disables authenticated read/write access, so blank logins receive the existing guest/read-only role when allow.read.only is enabled and are rejected when it is disabled.