Change ClusterTime to return BsonTimestamp instead of BsonDocument

Author: jsmurphy

src/MongoDB.Driver.Core/ChangeStreamDocument.cs

@@ -51,7 +51,7 @@ public ChangeStreamDocument(
         /// <value>
         /// The cluster time.
         /// </value>
-        public BsonDocument ClusterTime => GetValue<BsonDocument>(nameof(ClusterTime), null);
+        public BsonTimestamp ClusterTime => GetValue<BsonTimestamp>(nameof(ClusterTime), null);
 
         /// <summary>
         /// Gets the namespace of the collection.

src/MongoDB.Driver.Core/ChangeStreamDocumentSerializer.cs

@@ -40,7 +40,7 @@ public ChangeStreamDocumentSerializer(
         {
             _documentSerializer = Ensure.IsNotNull(documentSerializer, nameof(documentSerializer));
 
-            RegisterMember("ClusterTime", "clusterTime", BsonDocumentSerializer.Instance);
+            RegisterMember("ClusterTime", "clusterTime", BsonTimestampSerializer.Instance);
             RegisterMember("CollectionNamespace", "ns", ChangeStreamDocumentCollectionNamespaceSerializer.Instance);
             RegisterMember("DocumentKey", "documentKey", BsonDocumentSerializer.Instance);
             RegisterMember("FullDocument", "fullDocument", _documentSerializer);

tests/MongoDB.Driver.Core.Tests/ChangeStreamDocumentSerializerTests.cs

@@ -37,7 +37,7 @@ public void constructor_should_initialize_instance()
 
             result._documentSerializer().Should().BeSameAs(documentSerializer);
             result._memberSerializationInfo().Count.Should().Be(7);
-            AssertRegisteredMember(result, "ClusterTime", "clusterTime", BsonDocumentSerializer.Instance);
+            AssertRegisteredMember(result, "ClusterTime", "clusterTime", BsonTimestampSerializer.Instance);
             AssertRegisteredMember(result, "CollectionNamespace", "ns", ChangeStreamDocumentCollectionNamespaceSerializer.Instance);
             AssertRegisteredMember(result, "DocumentKey", "documentKey", BsonDocumentSerializer.Instance);
             AssertRegisteredMember(result, "FullDocument", "fullDocument", documentSerializer);

tests/MongoDB.Driver.Core.Tests/ChangeStreamDocumentTests.cs

@@ -75,7 +75,7 @@ public void BackingDocument_should_return_expected_result()
         [Fact]
         public void ClusterTime_should_return_expected_result()
         {
-            var value = new BsonDocument("x", 1234);
+            var value = new BsonTimestamp(DateTime.Now.Ticks);
             var backingDocument = new BsonDocument { { "other", 1 }, { "clusterTime", value } };
             var subject = CreateSubject(backingDocument: backingDocument);