Fix#30807
reuse functions in services
(cherry picked from commit a50026e2f30897904704895362da0fb12c7e5b26)
Conflicts:
models/issues/issue_update.go
routers/api/v1/repo/issue.go
trivial context conflict because of 'allow setting the update date on issues and comments'
(cherry picked from commit 6a4bc0289d)