add a test showing that unknown events are handled (#328)

We want to make sure unknown events from the engine (e.g. events that
are newly added) don't break the use of the automation API in dotnet.
Add a test to verify just that.

sdk/Pulumi.Automation.Tests/EventLogWatcherTests.cs

@@ -56,6 +56,15 @@ await Assert.ThrowsAsync<MyException>(async () =>
             });
         }
 
+        [Fact]
+        public async Task IgnoresUnknownEvents()
+        {
+            using var fx = new Fixture();
+            await fx.Write("{\"unknown\": \"event\"}");
+            await fx.Watcher.Stop();
+            Assert.Equal(1, fx.EventCounter);
+        }
+
         [Fact]
         public async Task PermitsUserInitiatedCancellation()
         {