feat:验证码（通用数字字母验证码）接口开发

xs-service/src/main/java/com/xiang/xservice/auth/service/service/CaptchaGenerateFactory.java

@@ -23,6 +23,10 @@ public class CaptchaGenerateFactory {
         if (Objects.isNull(type)) {
             return strategies.get(CaptchaTypeEnum.NORMAL_CAPTCHA_IMAGE.getType());
         }
-        return strategies.get(type);
+        ICaptchaService captchaService = strategies.get(type);
+        if (Objects.isNull(captchaService)) {
+            return strategies.get(CaptchaTypeEnum.NORMAL_CAPTCHA_IMAGE.getType());
+        }
+        return captchaService;
     }
 }