[ApiController]
[Route("api/[controller]")]
public class AttachmentsController : ControllerBase
{
    private readonly IWebHostEnvironment _env;
    public AttachmentsController(IWebHostEnvironment env) => _env = env;

    [HttpPost]
    public async Task<IActionResult> Upload([FromForm] IFormFileCollection files, [FromForm] int jobId)
    {
        var folder = Path.Combine(_env.ContentRootPath, "Attachments", jobId.ToString());
        Directory.CreateDirectory(folder);

        foreach (var file in files)
        {
            var path = Path.Combine(folder, file.FileName);
            using var stream = new FileStream(path, FileMode.Create);
            await file.CopyToAsync(stream);
        }

        return Ok();
    }
}