- Added `wait_start()` method that other threads can use to synchronize
with the engine and wait before performing db operations.
- Callback logic wrapped in a try/except block to prevent custom
integrations with buggy callbacks from crashing the engine.
- Support for an optional callback on `publish_entities` to get notified
when the published object are flushed to the db.
- Use `lazy='selectin'` for the entity parent -> children relationship -
it is more efficient and it ensures that all the data the application
needs is loaded upfront.
- `Entity.entity_key` rolled back to `<external_id, plugin>`. The
fallback logic on `<id, plugin>` created more problems than those it
as supposed to solve.
- Added `expire_on_commit=False` to the entities engine session to make
sure that we don't get errors on detached/expired instances.
- Better logic to recursively link parent/children entities, so partial
updates won't get lost.
- Removed `EntitiesCache` - it was too much to maintain while keeping
consistent with the ORM, and it was a perennial fight against
SQLAlchemy's own cache.
- Removed `EntityNotifier` - with no need to merge cached entities, the
`notify` method has become much simpler and it's simply been merged
in the `EntitiesRepository`.
Fabio Manganiello