Prevent several custom contribs with the same name

As a / an Studio user I want to Be prevented from creating several custom contribs with the same name so that I don't create messy configuration by mistake

AC
"Given I already have two custom contribs with the same name
When
Then Designer shows me a validation error on the correspondng contribs list:
Several contributions with the name [contrib name] are present.
"

"Given I create / rename a contrib
When I use the same name as an existing custom contrib
Then Designer shows me a validation error saying:
A contribution already exists with this name
and it prevents me from saving
"