+ Add translation support for backend by passing selected language in request header.

+ Add a new translation middleware.
+ Translated all /api/v1/system/* modules.
+ Translated /api/v1/autocode/auto_code_example.go
+ Increasing server timeout from 20 sec to 30 sec.
+ Fix Chinese translation for confirmation button.
+ Add selected language option to user store.

server/model/common/response/response.go

@@ -17,6 +17,7 @@ const (
 	SUCCESS = 0
 )
 
+// modified by mohamed hassan to support multilanguage
 func Result(code int, data interface{}, msg string, c *gin.Context) {
 	// 开始时间
 	c.JSON(http.StatusOK, Response{