Use action user as the trigger user of schedules (#30581)

Follow go-gitea/gitea#30357

When user push to default branch, the schedule trigger user will be the
user.
When disable then enable action units in settings, the schedule trigger
user will be action user.
When repo is a mirror, the schedule trigger user will be action user. (
before it will return error, fixed by #30357)

As scheduled job is a cron, the trigger user should be action user from
Gitea, not a real user.

---------

Co-authored-by: Giteabot <teabot@gitea.io>
(cherry picked from commit cb6814adad4dc81a683b50826a211ce7bce731d7)

Conflicts:
	- services/actions/notifier_helper.go
	  Conflict resolved by keeping Forgejo's version of the line.
(cherry picked from commit 829c3c6)

services/actions/notifier_helper.go

@@ -80,6 +80,11 @@ func newNotifyInput(repo *repo_model.Repository, doer *user_model.User, event we
 	}
 }
 
+func newNotifyInputForSchedules(repo *repo_model.Repository) *notifyInput {
+	// the doer here will be ignored as we force using action user when handling schedules
+	return newNotifyInput(repo, user_model.NewActionsUser(), webhook_module.HookEventSchedule)
+}
+
 func (input *notifyInput) WithDoer(doer *user_model.User) *notifyInput {
 	input.Doer = doer
 	return input
@@ -562,7 +567,7 @@ func DetectAndHandleSchedules(ctx context.Context, repo *repo_model.Repository)
 	// We need a notifyInput to call handleSchedules
 	// if repo is a mirror, commit author maybe an external user,
 	// so we use action user as the Doer of the notifyInput
-	notifyInput := newNotifyInput(repo, user_model.NewActionsUser(), webhook_module.HookEventSchedule)
+	notifyInput := newNotifyInputForSchedules(repo)
 
 	return handleSchedules(ctx, scheduleWorkflows, commit, notifyInput, repo.DefaultBranch)
 }