Allowing objectToFormData to be forced

[nickknissen]

For dotnet projects you have to specify the data binding type (json/form data).
Which makes it inconvenient to use a form where a a file is optional. Because you have to have multiple method for the same action.

Ex. multipart/form-data

[HttpPut("{id}")]
[Consumes("multipart/form-data")]
public async Task<IActionResult> UpdateFormData([FromForm] OrganizationViewModel viewModel, Guid id)
{
...

Ex. json

[HttpPut("{id}")]
[Consumes("application/json")]
public async Task<IActionResult> UpdateJson([FromBody] OrganizationViewModel viewModel, Guid id)
{
...

Allowing objectToFormData to be forced via options argument would help a lot with the boilerplate.

The change in inertia.js:

visit(url, {
    ....
    errorBag = null,
    forceFormData = false,
    onCancelToken = () => ({}),
    ...
  } = {}) {
    method = method.toLowerCase();
    [url, data] = mergeDataIntoQueryString(method, hrefToUrl(url), data)

    const visitHasFiles = hasFiles(data)
    if (forceFormData || method !== 'get' && visitHasFiles) {
      data = objectToFormData(data)
    }

Example usage:

this.form.post(this.route("organizations.store"), { forceFormData: true });

[claudiodekker]

@reinink Perhaps it would be a good idea to move the transform method out of the Form, and into the underlying visit?
That way, we don't have to introduce explicit support for specific edge cases like this while still solving the problem.

[reinink]

One way to solve this is to just manually do the FormData conversion yourself. That way it will always be sent as a multipart/form-data request, even if files are not present. That, obviously, doesn't help you take advantage of this feature of Inertia though.

[reinink]

I just put together a PR for this: #407