feat: add new_partitions field for CloseStream for Cloud Bigtable ChangeStream

protos/google/bigtable/v2/bigtable.proto

@@ -788,17 +788,37 @@ message ReadChangeStreamResponse {
   }
 
   // A message indicating that the client should stop reading from the stream.
-  // If status is OK and `continuation_tokens` is empty, the stream has finished
-  // (for example if there was an `end_time` specified).
-  // If `continuation_tokens` is present, then a change in partitioning requires
-  // the client to open a new stream for each token to resume reading.
+  // If status is OK and `continuation_tokens` & `new_partitions` are empty, the
+  // stream has finished (for example if there was an `end_time` specified).
+  // If `continuation_tokens` & `new_partitions` are present, then a change in
+  // partitioning requires the client to open a new stream for each token to
+  // resume reading. Example:
+  //                                  [B,      D) ends
+  //                                       |
+  //                                       v
+  //               new_partitions:  [A,  C) [C,  E)
+  // continuation_tokens.partitions:  [B,C) [C,D)
+  //                                  ^---^ ^---^
+  //                                  ^     ^
+  //                                  |     |
+  //                                  |     StreamContinuationToken 2
+  //                                  |
+  //                                  StreamContinuationToken 1
+  // To read the new partition [A,C), supply the continuation tokens whose
+  // ranges cover the new partition, for example ContinuationToken[A,B) &
+  // ContinuationToken[B,C).
   message CloseStream {
     // The status of the stream.
     google.rpc.Status status = 1;
 
-    // If non-empty, contains the information needed to start reading the new
-    // partition(s) that contain segments of this partition's row range.
+    // If non-empty, contains the information needed to resume reading their
+    // associated partitions.
     repeated StreamContinuationToken continuation_tokens = 2;
+
+    // If non-empty, contains the new partitions to start reading from, which
+    // are related to but not necessarily identical to the partitions for the
+    // above `continuation_tokens`.
+    repeated StreamPartition new_partitions = 3;
   }
 
   // The data or control message on the stream.