Notify user they won't have privileges to create branch when creating new project
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# Problem
Depending on a developers access, they may be able to create a new project, but won't have enough permissions to create a branch. This leads to wasted time and general confusion for users.
# Solution
Since we've decided (see references) that we won't fix this, we should at least notify a user before they click 'create project' that they'll need to request someone with maintainership/ownership of the project namespace to create a branch for them.
Bonus points if the tooltip/notification can tell the user who to contact.
Maybe make the button gray or have some indication they can not create a main branch.
### References
https://gitlab.com/gitlab-org/gitlab/-/issues/27566
https://gitlab.com/gitlab-org/gitlab/-/issues/25093
https://gitlab.com/gitlab-org/gitlab/-/issues/7583
https://gitlab.com/gitlab-org/gitlab/-/issues/30202
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