Add Cap Captcha support (#2511)

* Add Cap Captcha support

- Add CaptchaCap type constant in types.go
- Add Cap struct with InstanceURL, KeyID, and KeySecret fields
- Add CapCaptcha method in provider.go to return Cap settings
- Add default settings for Cap captcha in setting.go
- Implement Cap captcha verification logic in middleware
- Expose Cap captcha settings in site API

This adds support for Cap captcha service as an alternative
captcha option alongside existing reCAPTCHA, Turnstile and
built-in captcha options.

* update cap json tags

middleware/captcha.go

@@ -38,6 +38,9 @@ type (
 	turnstileResponse struct {
 		Success bool `json:"success"`
 	}
+	capResponse struct {
+		Success bool `json:"success"`
+	}
 )
 
 // CaptchaRequired 验证请求签名
@@ -127,6 +130,61 @@ func CaptchaRequired(enabled func(c *gin.Context) bool) gin.HandlerFunc {
 					return
 				}
 
+				break
+			case setting.CaptchaCap:
+				captchaSetting := settings.CapCaptcha(c)
+				if captchaSetting.InstanceURL == "" || captchaSetting.KeyID == "" || captchaSetting.KeySecret == "" {
+					l.Warning("Cap verification failed: missing configuration")
+					c.JSON(200, serializer.ErrWithDetails(c, serializer.CodeCaptchaError, "Captcha configuration error", nil))
+					c.Abort()
+					return
+				}
+
+				r := dep.RequestClient(
+					request2.WithContext(c),
+					request2.WithLogger(logging.FromContext(c)),
+					request2.WithHeader(http.Header{"Content-Type": []string{"application/json"}}),
+				)
+
+				capEndpoint := strings.TrimSuffix(captchaSetting.InstanceURL, "/") + "/" + captchaSetting.KeyID + "/siteverify"
+				requestBody := map[string]string{
+					"secret":   captchaSetting.KeySecret,
+					"response": service.Ticket,
+				}
+				requestData, err := json.Marshal(requestBody)
+				if err != nil {
+					l.Warning("Cap verification failed: %s", err)
+					c.JSON(200, serializer.ErrWithDetails(c, serializer.CodeCaptchaError, "Captcha validation failed", err))
+					c.Abort()
+					return
+				}
+
+				res, err := r.Request("POST", capEndpoint, strings.NewReader(string(requestData))).
+					CheckHTTPResponse(http.StatusOK).
+					GetResponse()
+				if err != nil {
+					l.Warning("Cap verification failed: %s", err)
+					c.JSON(200, serializer.ErrWithDetails(c, serializer.CodeCaptchaError, "Captcha validation failed", err))
+					c.Abort()
+					return
+				}
+
+				var capRes capResponse
+				err = json.Unmarshal([]byte(res), &capRes)
+				if err != nil {
+					l.Warning("Cap verification failed: %s", err)
+					c.JSON(200, serializer.ErrWithDetails(c, serializer.CodeCaptchaError, "Captcha validation failed", err))
+					c.Abort()
+					return
+				}
+
+				if !capRes.Success {
+					l.Warning("Cap verification failed: validation returned false")
+					c.JSON(200, serializer.ErrWithDetails(c, serializer.CodeCaptchaError, "Captcha validation failed", nil))
+					c.Abort()
+					return
+				}
+
 				break
 			}
 		}