WIP: Resolve "HTTPS based deploy keys (deploy tokens)"

What does this MR do?

Implements deploy tokens (#20845 (moved))

Are there points in the code the reviewer needs to double check?

Since this is auth* related it needs to be reviewed and picked over with the utmost scrutiny.

Why was this MR needed?

Access per project akin to that of ssh key based access is a a requirement of customers and found to be useful by the community.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

• Issue #20845 (moved)

Closes #20845 (moved)