Improve uploader client connection and diagnostics

clients/photobooth-uploader/PhotoboothUploader/Models/PhotoboothConnectResponse.cs

@@ -13,6 +13,9 @@ public sealed class PhotoboothConnectResponse
 
 public sealed class PhotoboothConnectPayload
 {
+    [JsonPropertyName("event_name")]
+    public string? EventName { get; set; }
+
     [JsonPropertyName("upload_url")]
     public string? UploadUrl { get; set; }