Callback's first argument is an optional Error now. Was: required `any`.
PersistedModel methods return `PersistedModel` now. Before this change,
methods were returning `PersistedData` (`PersistedModel | AnyObject`).
The problem with `AnyObject` is that it does not contain any
`PersistedModel` instance data and cannot be assigned to functions
expecting `Partial<PersistedModel>`. As a result, consumers of this API
were forced to either cast the result to `PersistedModel` (which feels
wrong) or deal with the `AnyObject` case (which never happen at
runtime).
Fix definition of `ModelData<T>` to `T | Partial<T>`. Before this
change, `ModelData` allowed any values not related to the actual
model at all, for example arrays.
Use case:
1. Configure a datasource with lazyConnect = true
2. Do NOT start the DB
3. Start the app
4. Send first request and it fails to connnect to the DB
5. Start the DB
5. Requests are now served correctly