If you want to activate the relay bot in a room, use `!signal set-relay`.
Use `!signal unset-relay` to deactivate.
Additionally the permissions for the bridge grant user rights to all base domain users in case the relay bot is disabled, or relay rights in case the relay bot is enabled.
By default, any user on your homeserver will be able to use the bridge.
If you enable the relay bot functionality, it will relay every user's messages in a portal room - no matter which homeserver they're from.
If you would like to have a more specific setting of the permissions you can set the permissions as follows (example). For more details see also [mautrix-bridge documentation](https://docs.mau.fi/bridges/python/signal/relay-mode.html)