If a custom typecasting is needed, easy, simply register own type in DBAL. If a library wants to provide some custom types by default, bootstrap (register on load time) using composer.

I think this is step in a good direction, as we can then leave all typecasting to standard DBAL Types and remove all hacky typing from the code. DBAL Types can also be easily replaced and/or a new/custom Type can be easily added.

• yes, this will solve all typecasting across different Persistences
• this PR is strictly focused on typecasting a managed value (php value) to an unmanaged value (string, scalar in general)
• this PR is BC as much as possible, ie. it keep working without explicit Persistence nor Platform

BC breaks:

• removed Field::serialize property, to use PHP serialization, use object type.
• removed Field::typecast property, to use a custom typecasting, extend the target DBAL type class and register it or implement a custom persistence
• removed Field::dateTimeClass/dateTimeZoneClass properties, see bullet point above
• removed Field::persist_format/persist_timezone properties, see above, but you probably want to handle it using persistence/UI solely - if there was a shared format/TZ, different format/TZ was not possible to set for the database and UI
• removed Model::strict_types property, was already enabled by default, normalization can still be disabled/broken by Model::HOOK_NORMALIZE hook
• array type is temporary forbidden to be used, object type now serializes data using PHP serialization, to use JSON, use json type. For more details, see the following table: