How to enable cross-signed for the client?

[mwnu]

There is a warning in the logs:

WARNING client/[@name:domain.com](https://matrix.to/#/@name:domain.com)/crypto Device [@name:domain.com](https://matrix.to/#/@name:domain.com)/client1 isn't cross-signed.

link:https://github.com/maubot/maubot/issues/244