Return access_denied error when an OAuth2 request is denied (#30974) (#31029)

Backport #30974 by Zettat123

Co-authored-by: Zettat123 <zettat123@gmail.com>
Co-authored-by: KN4CK3R <admin@oldschoolhack.me>

services/forms/user_form.go

@@ -161,6 +161,7 @@ func (f *AuthorizationForm) Validate(req *http.Request, errs binding.Errors) bin
 // GrantApplicationForm form for authorizing oauth2 clients
 type GrantApplicationForm struct {
 	ClientID    string `binding:"Required"`
+	Granted     bool
 	RedirectURI string
 	State       string
 	Scope       string