[refactor] replace int with httpStatusCodes (#15282)

* replace "200" (int) with "http.StatusOK" (const)

* ctx.Error & ctx.HTML

* ctx.JSON Part1

* ctx.JSON Part2

* ctx.JSON Part3

modules/context/context.go

@@ -213,7 +213,7 @@ func (ctx *Context) RenderWithErr(msg string, tpl base.TplName, form interface{}
 	}
 	ctx.Flash.ErrorMsg = msg
 	ctx.Data["Flash"] = ctx.Flash
-	ctx.HTML(200, tpl)
+	ctx.HTML(http.StatusOK, tpl)
 }
 
 // NotFound displays a 404 (Not Found) page and prints the given error, if any.