I'm trying to create a file upload endpoint, but it looks like the only requests that get through have to specify `application/json` as the content type. Here is what my endpoint looks like:

```
[HttpPost()]
public async Task<IActionResult> CreateFile([FromBody] IFormFile contents)

```

I'm running .NET Core 2.0, and my startup.cs is pretty much just stock. What am I doing wrong?