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>

services/forms/repo_form.go

@@ -10,7 +10,6 @@ import (
 
 	issues_model "code.gitea.io/gitea/models/issues"
 	project_model "code.gitea.io/gitea/models/project"
-	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/web/middleware"
 	"code.gitea.io/gitea/services/context"
@@ -473,22 +472,6 @@ func (i *IssueLockForm) Validate(req *http.Request, errs binding.Errors) binding
 	return middleware.Validate(errs, ctx.Data, i, ctx.Locale)
 }
 
-// HasValidReason checks to make sure that the reason submitted in
-// the form matches any of the values in the config
-func (i IssueLockForm) HasValidReason() bool {
-	if strings.TrimSpace(i.Reason) == "" {
-		return true
-	}
-
-	for _, v := range setting.Repository.Issue.LockReasons {
-		if v == i.Reason {
-			return true
-		}
-	}
-
-	return false
-}
-
 // CreateProjectForm form for creating a project
 type CreateProjectForm struct {
 	Title        string `binding:"Required;MaxSize(100)"`