Improve uploader client connection and diagnostics

clients/photobooth-uploader/PhotoboothUploader/Services/UploadService.cs

@@ -12,10 +12,20 @@ namespace PhotoboothUploader.Services;
 
 public sealed class UploadService
 {
+    private static readonly TimeSpan DefaultTimeout = TimeSpan.FromSeconds(20);
     private readonly Channel<string> _queue = Channel.CreateUnbounded<string>();
     private readonly ConcurrentDictionary<string, byte> _pending = new(StringComparer.OrdinalIgnoreCase);
+    private string _userAgent = "FotospielPhotoboothUploader";
     private CancellationTokenSource? _cts;
 
+    public void Configure(string userAgent)
+    {
+        if (!string.IsNullOrWhiteSpace(userAgent))
+        {
+            _userAgent = userAgent;
+        }
+    }
+
     public void Start(
         PhotoboothSettings settings,
         Action<string> onQueued,
@@ -61,6 +71,9 @@ public sealed class UploadService
         }
 
         using var client = new HttpClient();
+        client.Timeout = DefaultTimeout;
+        client.DefaultRequestHeaders.UserAgent.ParseAdd(_userAgent);
+        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
 
         while (await _queue.Reader.WaitToReadAsync(token))
         {