Expose CODEOWNERS rules via API
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### Proposal
Build a API endpoint (REST or GraphQL) to expose CODEOWNERS information.
This would be useful for integrations with external systems as well as to build summary information within GitLab itself, as noted on https://gitlab.com/gitlab-org/gitlab/-/issues/389091+
> will allow for the of APIs that integrate permissions with branch rules for external consumption
We may want to expand the scope of this to include other permissions around branches and rules.
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issue