refactor(net): own session wiring subscriptions

tests/AcDream.Core.Net.Tests/SubscriptionSetTests.cs

@@ -0,0 +1,47 @@
+namespace AcDream.Core.Net.Tests;
+
+public sealed class SubscriptionSetTests
+{
+    [Fact]
+    public void Dispose_ReleasesInReverseOrderAndIsIdempotent()
+    {
+        var order = new List<int>();
+        var subscriptions = new SubscriptionSet();
+        subscriptions.Add(() => order.Add(1));
+        subscriptions.Add(() => order.Add(2));
+        subscriptions.Add(() => order.Add(3));
+
+        subscriptions.Dispose();
+        subscriptions.Dispose();
+
+        Assert.Equal([3, 2, 1], order);
+    }
+
+    [Fact]
+    public void Dispose_AttemptsEveryReleaseAndAggregatesFailures()
+    {
+        var order = new List<int>();
+        var subscriptions = new SubscriptionSet();
+        subscriptions.Add(() => order.Add(1));
+        subscriptions.Add(() =>
+        {
+            order.Add(2);
+            throw new InvalidOperationException("second failed");
+        });
+        subscriptions.Add(() =>
+        {
+            order.Add(3);
+            throw new IOException("third failed");
+        });
+
+        AggregateException error = Assert.Throws<AggregateException>(
+            subscriptions.Dispose);
+
+        Assert.Equal([3, 2, 1], order);
+        Assert.Collection(
+            error.InnerExceptions,
+            exception => Assert.IsType<IOException>(exception),
+            exception => Assert.IsType<InvalidOperationException>(exception));
+        subscriptions.Dispose();
+    }
+}