Port `EventInternalMetadata` class to Rust (#16782)

There are a couple of things we need to be careful of here:

1. The current python code does no validation when loading from the DB,
so we need to be careful to ignore such errors (at least on jki.re there
are some old events with internal metadata fields of the wrong type).
2. We want to be memory efficient, as we often have many hundreds of
thousands of events in the cache at a time.

---------

Co-authored-by: Quentin Gliech <quenting@element.io>

1 files changed, 3 insertions, 2 deletions

diff --git a/tests/storage/test_redaction.py b/tests/storage/test_redaction.py

index c88ec69c94..cb459d6b03 100644
--- a/tests/storage/test_redaction.py
+++ b/tests/storage/test_redaction.py
@@ -25,9 +25,10 @@ from twisted.test.proto_helpers import MemoryReactor
 
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.room_versions import RoomVersions
-from synapse.events import EventBase, _EventInternalMetadata
+from synapse.events import EventBase
 from synapse.events.builder import EventBuilder
 from synapse.server import HomeServer
+from synapse.synapse_rust.events import EventInternalMetadata
 from synapse.types import JsonDict, RoomID, UserID
 from synapse.util import Clock
 
@@ -268,7 +269,7 @@ class RedactionTestCase(unittest.HomeserverTestCase):
                 return self._base_builder.type
 
             @property
-            def internal_metadata(self) -> _EventInternalMetadata:
+            def internal_metadata(self) -> EventInternalMetadata:
                 return self._base_builder.internal_metadata
 
         event_1, unpersisted_context_1 = self.get_success(