Add API to get merged PR of a commit (#29243)

Adds a new API `/repos/{owner}/{repo}/commits/{sha}/pull` that allows
you to get the merged PR associated to a commit.

---------

Co-authored-by: 6543 <6543@obermui.de>

routers/api/v1/api.go

@@ -1235,6 +1235,7 @@ func Routes() *web.Route {
 					m.Group("/{ref}", func() {
 						m.Get("/status", repo.GetCombinedCommitStatusByRef)
 						m.Get("/statuses", repo.GetCommitStatusesByRef)
+						m.Get("/pull", repo.GetCommitPullRequest)
 					}, context.ReferencesGitRepo())
 				}, reqRepoReader(unit.TypeCode))
 				m.Group("/git", func() {