Add flag to enable alchemysession core mode

example-config.yaml

@@ -27,6 +27,9 @@ appservice:
     #   SQLite:   sqlite:///filename.db
     #   Postgres: postgres://username:password@hostname/dbname
     database: sqlite:///mautrix-telegram.db
+    # Whether or not to use SQLAlchemy Core for common database actions. Use if the bridge is
+    # being bottlenecked on ORM commits. Only supported with PostgreSQL.
+    sqlalchemy_core_mode: false
 
     # Public part of web server for out-of-Matrix interaction with the bridge.
     # Used for things like login if the user wants to make sure the 2FA password isn't stored in