basic skeleton for the API and queueing

MalwareMultiScan.Api/Controllers/DownloadController.cs

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+using System.Threading.Tasks;
+using MalwareMultiScan.Api.Services;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+
+namespace MalwareMultiScan.Api.Controllers
+{
+    [Route("download")]
+    public class DownloadController : Controller
+    {
+        private readonly ScanResultsService _scanResultsService;
+
+        public DownloadController(ScanResultsService scanResultsService)
+        {
+            _scanResultsService = scanResultsService;
+        }
+
+        [HttpGet("{id}")]
+        [ProducesResponseType(StatusCodes.Status200OK)]
+        [ProducesResponseType(StatusCodes.Status404NotFound)]
+        public async Task<IActionResult> Index(string id)
+        {
+            var fileStream = await _scanResultsService.ObtainFile(id);
+
+            if (fileStream == null)
+                return NotFound();
+
+            return File(fileStream, "application/octet-stream");
+        }
+    }
+}