Merge pull request #25334 from rhcs-dashboard/rgw-email-validation

mgr/dashboard: Validation for duplicate RGW user email

Reviewed-by: Alfonso Martínez <almartin@redhat.com>
Reviewed-by: Laura Paduano <lpaduano@suse.com>

diff --cc src/pybind/mgr/dashboard/frontend/src/locale/messages.xlf
Simple merge