Issue a verified sender again only over the membership that was read, so a newer push is not overwritten (issue 930)

internal/link/bus.go

@@ -179,6 +179,19 @@ func (b OverNATS) PublishMembership(ctx context.Context, node, module string, bo
 	return nil
 }
 
+// PublishMembershipAfter issues a membership only if the one read at sequence seq is still the newest of its
+// subject: a push that issued another since is not overwritten, and the refusal comes back (novox/hq issue 930).
+func (b OverNATS) PublishMembershipAfter(ctx context.Context, node, module string, body []byte, seq uint64) error {
+	ctx, cancel := context.WithTimeout(ctx, MembershipWait)
+	defer cancel()
+	_, err := b.JS.Publish(broker.MembershipSubject(node, module), body, nats.Context(ctx),
+		nats.ExpectLastSequencePerSubject(seq))
+	if err != nil {
+		return fmt.Errorf("issuing %s on %s its membership after sequence %d: %w", module, node, seq, err)
+	}
+	return nil
+}
+
 func (b OverNATS) PublishDeclaration(ctx context.Context, node string, body []byte) error {
 	_, err := b.JS.Publish(DeclareSubject(node), body, nats.Context(ctx))
 	if err != nil {