feat(binding): support custom struct tag (#2720)

* feat(binding): support custom struct tag

Add function `binding.MapFormWithTag` (#2719)

* doc: add 'bind form-data with custom struct tag'

Add 'Bind form-data request with custom struct and custom tag' section (#2719)

* test(binding): add test for MapFromWithTag

binding/form_mapping.go

@@ -34,6 +34,10 @@ func mapForm(ptr interface{}, form map[string][]string) error {
 	return mapFormByTag(ptr, form, "form")
 }
 
+func MapFormWithTag(ptr interface{}, form map[string][]string, tag string) error {
+	return mapFormByTag(ptr, form, tag)
+}
+
 var emptyField = reflect.StructField{}
 
 func mapFormByTag(ptr interface{}, form map[string][]string, tag string) error {