Add support mCaptcha as captcha provider (#20458)

https://mcaptcha.org/

Co-authored-by: Felipe Leopoldo Sologuren Gutiérrez <fsologureng@users.noreply.github.com>

modules/mcaptcha/mcaptcha.go

@@ -0,0 +1,27 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package mcaptcha
+
+import (
+	"context"
+	"fmt"
+
+	"code.gitea.io/gitea/modules/setting"
+
+	"codeberg.org/gusted/mcaptcha"
+)
+
+func Verify(ctx context.Context, token string) (bool, error) {
+	valid, err := mcaptcha.Verify(ctx, &mcaptcha.VerifyOpts{
+		InstanceURL: setting.Service.McaptchaURL,
+		Sitekey:     setting.Service.McaptchaSitekey,
+		Secret:      setting.Service.McaptchaSecret,
+		Token:       token,
+	})
+	if err != nil {
+		return false, fmt.Errorf("wasn't able to verify mCaptcha: %v", err)
+	}
+	return valid, nil
+}