feat: support configurable captcha(reCaptcha & hCaptcha) (#765)

* feat: support configurable captcha(layered architecture)

* refactor & add captcha logo

* rename captcha

* Update authz.go

* Update hcaptcha.go

* Update default.go

* Update recaptcha.go

Co-authored-by: Gucheng <85475922+nomeguy@users.noreply.github.com>

captcha/hcaptcha.go

@@ -0,0 +1,60 @@
+// 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 captcha
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+)
+
+const HCaptchaVerifyUrl = "https://hcaptcha.com/siteverify"
+
+type HCaptchaProvider struct {
+}
+
+func NewHCaptchaProvider() *HCaptchaProvider {
+	captcha := &HCaptchaProvider{}
+	return captcha
+}
+
+func (captcha *HCaptchaProvider) VerifyCaptcha(token, clientSecret string) (bool, error) {
+	reqData := url.Values{
+		"secret":   {clientSecret},
+		"response": {token},
+	}
+	resp, err := http.PostForm(HCaptchaVerifyUrl, reqData)
+	if err != nil {
+		return false, err
+	}
+
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return false, err
+	}
+
+	type captchaResponse struct {
+		Success bool `json:"success"`
+	}
+	captchaResp := &captchaResponse{}
+	err = json.Unmarshal(body, captchaResp)
+	if err != nil {
+		return false, err
+	}
+
+	return captchaResp.Success, nil
+}