14898 all developers can push to protected branch by default

This MR protects protected branches from developers when not given the permission to push to them. Before it was possible to do this if the repository was empty and you could create a README/LICENSE/.gitignore/etc and it would've created a new master branch protected by default. With this it is not possible to do it anymore.

• [x ] CHANGELOG entry added
• Tests
  • [x ] Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together Closes #14898 (closed)