* Add branch protection option to block merge on requested changes.

* Add migration step

* Fix check to correct negation

* Apply suggestions from code review

Language improvement.

Co-Authored-By: John Olheiser <42128690+jolheiser@users.noreply.github.com>

* Copyright year.

Co-authored-by: John Olheiser <42128690+jolheiser@users.noreply.github.com>
Co-authored-by: Lauris BH <lauris@nix.lv>

Add an option to protected branches to add writing deploy keys to the whitelist for pushing.

Please note this is technically a breaking change: previously if the owner of a repository was on the whitelist then any writing deploy key was effectively on the whitelist. This option will now need to be set if that is desired.

Closes #8472 

Details:
* Allow Protected Branches to Whitelist Deploy Keys
* Add migration
* Ensure that IsDeployKey is set to false on the http pushes
* add not null default false