Branch rules MVC: Design or reuse the database schema to store Branch rules

Problem

We need to store information about Branch Rules in database

This issue blocks #362706 (closed), #362707 (closed), #362219 (closed)

Proposal

I see two possible options to proceed

1. Create a new table for Branch Rules and add necessary code to the Rails app
2. Reuse protected_branches table for keeping Branch rules data

It is an investigation issue, we need to evaluate both options and decide how to proceed next.

Implementation plan

issue	note
Branch rules MVC: Implement frontend skeleton (#362205 - closed)
Implement the ability to add branch Protections (#362212 - closed)
Implement the ability to add Merge Request appr... (#362214 - closed)
Branch rules MVC: Design or reuse the database ... (#362705 - closed)	👈 this issue
Branch rules MVC: Add GraphQL endpoint to suppo... (#362706 - closed)	⚠ blocked by #362705 (closed)
Branch rules MVC: Add GraphQL endpoint to updat... (#362707 - closed)	⚠ blocked by #362705 (closed)
Branch rules MVC: Add GraphQL endpoint to delet... (#362219 - closed)	⚠ blocked by #362705 (closed)
Branch rules MVC: List branch rules under Repos... (#362217 - closed)	⚠ blocked by #362219 (closed)
Implement the ability to Delete a Branch rule (#362218 - closed)	⚠ blocked by #362219 (closed)

Additional areas affected

1. Import/Export currently include protected branches