Fixes the Android Login process

src/PostIt/PostIt.Android/Services/OidcCallbackManager.cs

@@ -0,0 +1,21 @@
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace PostIt.Droid.Services;
+
+public static class OidcCallbackManager
+{
+    private static TaskCompletionSource<string>? _tcs;
+
+    public static Task<string> RegisterCallback(CancellationToken cancellationToken)
+    {
+        _tcs = new TaskCompletionSource<string>();
+        cancellationToken.Register(() => _tcs.TrySetCanceled());
+        return _tcs.Task;
+    }
+
+    public static void SetResult(string url)
+    {
+        _tcs?.TrySetResult(url);
+    }
+}