Small fixes

Author: papafe

src/MongoDB.Bson/Serialization/Serializers/BsonClassMapSerializer.cs

@@ -326,6 +326,11 @@ public bool GetDocumentId(
             out object id,
             out Type idNominalType,
             out IIdGenerator idGenerator)
+            => GetDocumentId(document, BsonSerializer.DefaultDomain, out id, out idNominalType, out idGenerator);
+
+        /// <inheritdoc/>
+        public bool GetDocumentId(object document, IBsonSerializationDomain domain, out object id, out Type idNominalType,
+            out IIdGenerator idGenerator)
         {
             var idMemberMap = _classMap.IdMemberMap;
             if (idMemberMap != null)

src/MongoDB.Driver/OfTypeSerializer.cs

@@ -45,7 +45,12 @@ obj is OfTypeSerializer<TRootDocument, TDerivedDocument> other &&
                 object.Equals(_derivedDocumentSerializer, other._derivedDocumentSerializer);
         }
 
-        public bool GetDocumentId(object document, out object id, out Type idNominalType, out IIdGenerator idGenerator)
+        public bool
+            GetDocumentId(object document, out object id, out Type idNominalType, out IIdGenerator idGenerator)
+                => GetDocumentId(document, BsonSerializer.DefaultDomain, out id, out idNominalType, out idGenerator);
+
+        public bool GetDocumentId(object document, IBsonSerializationDomain domain, out object id, out Type idNominalType,
+            out IIdGenerator idGenerator)
         {
             if (_derivedDocumentSerializer is IBsonIdProvider idProvider)
             {