Feature request: Support tls ca change propagation to DatabaseRequires

This issue outlines a feature request for supporting tls change propagation for apps on the `DatabaseRequires` side of the relation.

Currently, the `tls-ca` and `tls` info is only passed on the `DatabaseCreatedEvent` which is triggered once during database relation setup. However, when tls is later configured or changed, there is currently no propagation of such event towards the application side. However, when working with self-signed certificates, the certificates may need to be added to the trusted root ca, hence the requirement for the change to be propagated.

Thank you very much! :)