fix: token endpoint supports json format (#641)

Signed-off-by: Steve0x2a <stevesough@gmail.com>

controllers/types.go

@@ -0,0 +1,26 @@
+// Copyright 2022 The Casdoor Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package controllers
+
+type TokenRequest struct {
+	GrantType    string `json:"grant_type"`
+	Code         string `json:"code"`
+	ClientId     string `json:"client_id"`
+	ClientSecret string `json:"client_secret"`
+	Verifier     string `json:"code_verifier"`
+	Scope        string `json:"scope"`
+	Username     string `json:"username"`
+	Password     string `json:"password"`
+}