docs(api): add model option formData

Author: JoaoPedroAS51

docs/content/en/api/model-options.md

@@ -65,6 +65,24 @@ parameterNames() {
 }
 ```
 
+### `formData`
+- Returns: `object`
+
+This method can be overridden in the model to configure `object-to-formdata`.
+
+See [object-to-formdata](https://github.com/therealparmesh/object-to-formdata#usage)
+
+```js
+formData() {
+  return {
+    indices: false,
+    nullsAsUndefineds: false,
+    booleansAsIntegers: false,
+    allowEmptyArrays: false,
+  }
+}
+```
+
 #### `include`
 - Default: `include`
 - Returns: `string`