When the ldap synchronizer is look for an email address and fails at
finding one, it falls back at creating one using "localhost.local"
domain.
This new field makes this domain name configurable.
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/3414
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Baptiste Daroussin <bapt@FreeBSD.org>
Co-committed-by: Baptiste Daroussin <bapt@FreeBSD.org>
