Merge branch '611-custom-overlays' into 'devel_12.1.x'

Resolve "disable "Add overlay" button or improve error message `403` when number of custom layout is greater equal `CUSTOM_LAYOUTS`"

See merge request !572
9 jobs for v12.1.5 in 15 minutes and 44 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #43134
privileged
build_war

00:03:40

 
  Packaging
passed #43135
privileged
build_debian_package

00:07:43

passed #43136
privileged
build_rpm

00:01:18

 
  Test
passed #43139
privileged
rpmlint

00:00:32

passed #43140
privileged
test_deploy_with_db_without_superadmin_rights

00:00:57

passed #43137
test_frontend

00:01:57

passed #43777
privileged
test_install_debian_package

00:02:22

passed #43602
privileged
test_install_debian_package

00:02:17

passed #43138
privileged
test_install_debian_package

00:02:25