Improve space dialog creation when restricted space key already exists

Summary

In Confluence, when creating a space with a key/title that already exists, the same will display the following message:

A space with this space key already exists.

However, in situations where a space containing the already existing key is restricted, Confluence will not have a message about its existence. The create button will only remain "greyed out".

In situations like this one, it would be helpful if Confluence could provide a message about some impossibility to create the space, but, not necessarily exposing the existing space key.