Store named datetime columns as INTEGER microseconds (datetime_columns)

src/sqlmem/engine.py

@@ -66,6 +66,7 @@ class CachingEngine:
         fetch_batch: int | None = None,
         dialect: str | None = None,
         pragmas: dict[str, str | int] | None = None,
+        datetime_columns: dict[str, list[str]] | None = None,
         blocking_startup_refresh: bool = False,
     ) -> None:
         self._source_engine = source_engine
@@ -81,6 +82,7 @@ class CachingEngine:
             dialect=self._dialect,
             fetch_batch=fetch_batch if fetch_batch is not None else FETCH_BATCH_SIZE,
             pragmas=pragmas,
+            datetime_columns=datetime_columns,
         )
         self._registry = ColumnRegistry(self._cache.connection)
         self._stats = StatsCollector()