API to recursively apply group-level push rules to existing projects
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### Problem to solve
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We introduced group-level push rules in https://gitlab.com/gitlab-org/gitlab/-/issues/34370, but when applied they do not recursively and retroactively apply to existing projects. Newly created projects within the root group's hierarchy appropriately inherit these rules, but existing rules can number in the thousands and be a headache to update individually.
### Intended users
* [Cameron (Compliance Manager)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#cameron-compliance-manager)
* [Sidney (Systems Administrator)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sidney-systems-administrator)
### JTBD
When I have configured push rules at a group level, I want a single action that applies those rules to all existing projects, so that my entire namespace is brought into compliance with these push rules without me having to manually update every single subgroup and project.
### User experience goal
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Cameron or Sidney no longer has to dig into projects to understand which ones have differing push rules and manually update those settings to match their parent group.
### Proposal
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Add an API endpoint to the [Group Push Rules API](https://docs.gitlab.com/ee/api/groups.html#push-rules) that allows a `group owner` to recursively inherit the push rules down into each subgroup and project.
* _Consider leveraging the existing [Project Push Rules API](https://docs.gitlab.com/ee/api/projects.html#push-rules)_
### Further details
<!-- Include use cases, benefits, goals, or any other details that will help us understand the problem better. -->
**Use Case:** Groups may be discovering their workflows, resulting in many, frequent changes to settings such as push rules. This requires manual updates to each project or building custom tooling to automate this process.
### Permissions and Security
<!-- What permissions are required to perform the described actions? Are they consistent with the existing permissions as documented for users, groups, and projects as appropriate? Is the proposed behavior consistent between the UI, API, and other access methods (e.g. email replies)?-->
### Documentation
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### Availability & Testing
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What risks does this change pose to our availability? How might it affect the quality of the product? What additional test coverage or changes to tests will be needed? Will it require cross-browser testing?
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* Unit test changes
* Integration test changes
* End-to-end test change
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### What does success look like, and how can we measure that?
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We can measure this by reaching out to customers and asking how this feature is helping or if it is lacking.
### What is the type of buyer?
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### Is this a cross-stage feature?
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