This PR is part of #4767. It contains
* a refactoring of validation error messages
* adds the ability to send user-activities to distant federated servers
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8792
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Michael Jerger <michael.jerger@meissa-gmbh.de>
Co-committed-by: Michael Jerger <michael.jerger@meissa-gmbh.de>
