Add API routes to lock and unlock issues (#34165)

This pull request adds a GitHub-compatible API endpoint to lock and
unlock an issue.

The following routes exist now:
- `PUT /api/v1/repos/{owner}/{repo}/issues/{id}/lock` to lock an issue
- `DELETE /api/v1/repos/{owner}/{repo}/issues/{id}/lock` to unlock an issue

Fixes #33677
Fixes #20012

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/issue_lock.go

@@ -24,11 +24,6 @@ func LockIssue(ctx *context.Context) {
 		return
 	}
 
-	if !form.HasValidReason() {
-		ctx.JSONError(ctx.Tr("repo.issues.lock.unknown_reason"))
-		return
-	}
-
 	if err := issues_model.LockIssue(ctx, &issues_model.IssueLockOptions{
 		Doer:   ctx.Doer,
 		Issue:  issue,