Password Requirements: Common Phrases

We should be changing the password input field for every instance of GitLab (.com and self-managed) as pointed out in #458441 (comment 1896743006).

Figma link has designs for all registrations.

We should tell the user about any password conditions at the start, which will ultimately help the user to create a more secure account.

Updated copy to replace "Minimum length is 8 characters":

• Cannot use common phrases (e.g. “password”)\

Techical details

• Add an API request on password input change (by analogy with the username).
• Add new controller with single endpoint under app/controllers/users/....
• Rename Security::WeakPasswords.weak_for_user? to weak_errors or similar and make it return the list of errors instead of true/false to be useful on the frontend part.
• Use existing design for the password requirements list:

Can be enabled in admin panel: