Approval Rules landing page
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### Problem to solve
Branch and approval rule documentation is presented on a number of pages, and there is no "roadmap" that ties them all together. It's not clear how each feature or sub-feature interacts.
- [Push Rules](https://docs.gitlab.com/ee/user/project/repository/push_rules.html)
- [Code Owners](https://docs.gitlab.com/ee/user/project/codeowners/)
- [Manage and Protect Branches](https://docs.gitlab.com/ee/user/project/repository/branches/#manage-and-protect-branches)
- [Default Branch protections](https://docs.gitlab.com/ee/user/project/repository/branches/default.html)
- [Protected Branches](https://docs.gitlab.com/ee/user/project/protected_branches.html)
- [Merge Request approval rules](https://docs.gitlab.com/ee/user/project/merge_requests/approvals/rules.html)
- [Security Approvals](https://docs.gitlab.com/ee/user/project/merge_requests/approvals/rules.html#security-approvals)
- [Status checks](https://docs.gitlab.com/ee/user/project/merge_requests/status_checks.html)
- [List branch rules for a project (GraphQL API)](https://docs.gitlab.com/ee/api/graphql/branch_rules.html)
### Code entry points
#### Git Push
- Push Rules
#### Edit code in UI
- Push Rules?
#### When a MR is created
- Codeowners ?
#### When a MR is merged
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### Proposal
- Create a high level overview of how all these features work together
- Cross-link existing pages.
### Who can address the issue
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### Other links/references
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issue