GrapeDSL for branches endpoints

No changelog item as it doesn't change behaviour Cherry-picket from !6330 (closed)

@zj LGTM Builds are not passing, please rebase on master.

Reassigned to @zj

Added 112 commits:

• 735a21ad...a1aea326 - 111 commits from branch master
• 45845279 - GrapeDSL for branches endpoints

Rebased, I just assume the tests will pass so Ill take the liberty to reassign to an endboss.

Reassigned to @rymai

Mentioned in issue #22928 (moved)

Added ~13884 label

Added 7 commits:

• 45845279...4be63f5b - 6 commits from branch master
• 7817b35d - GrapeDSL for branches endpoints

Milestone changed to %8.13

Marked this merge request as a Work In Progress

Resolved all discussions

Added 1752 commits:

• 7817b35d...51821e1e - 1751 commits from branch master
• 18e693aa - GrapeDSL for branches endpoints

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@rymai I've rebased this, and this should be ready to be merged. Let me know if you agree or have remarks.

Unmarked this merge request as a Work In Progress

Added 1 commit:

• 308b3226 - GrapeDSL for branches endpoints

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Thanks @zj, I had a few questions/notes.