Add MultiWriterIdGenerator. (#7281)

This will be used to coordinate stream IDs across multiple writers.

Functions as the equivalent of both `StreamIdGenerator` and
`SlavedIdTracker`.

1 files changed, 1 insertions, 0 deletions

diff --git a/tox.ini b/tox.ini

index eccc44e436..4a1509c51b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -203,6 +203,7 @@ commands = mypy \
             synapse/storage/data_stores/main/ui_auth.py \
             synapse/storage/database.py \
             synapse/storage/engines \
+            synapse/storage/util \
             synapse/streams \
             synapse/util/caches/stream_change_cache.py \
             tests/replication/tcp/streams \