[GH-8327] Deprecate EntityManagerHelper for a provider abstraction.

[beberlei]

Deprecates the EntityManagerHelper in favor of a new EntityManagerProvider interface that comes with two implementation.

• A BC abstraction wrapping the Console HelperSet HelpersetManagerProvider
• a new SingleManagerProvider that provides access to a single entity manager.

In addition an implementation for the DBAL ConnectionProvider is provided that is based on any EntityManagerProvider and calling getConnection() on the EntityManager.

It is expected for the DoctrineBundle to create a new EntityManagerProvider that provides access to their multiple ORM entity managers via the Symfony DI Container.

Two deprecation messages are added:

• When the HelperSetManagerProvider must be used from within ConsoleRunner, because a HelperSet is passed.
• When an ORM command is used without explicitly passing the EntityManagerProvider as a dependency.

Todos:

• Sort out update of DBAL and 7.2 dependency, waiting for Reintroduce support for PHP 7.1 and 7.2 dbal#4386
• Update tests to pass provider

Fixes #8327

[greg0ire]

Is it possible that people define several managers but end up using SingleManagerProvider? If yes, that exception will be confusing I think.

[greg0ire]

Also, let's test this?

[beberlei]

No the SingleManagerProvider is for non Symfony context, where usually you have only one and you don't care about any of this. :)

[greg0ire]

LGTM. The code suggestions I added are just that: suggestions

[dominikzogg]

@beberlei adding em option probably breaks every glue code out there similar to the doctrine bundle. This change should be in 3.0 not 2.9

[beberlei]

@dominikzogg we speifically added code to prevent breaking in doctrine Bundle

[beberlei]

doctrine/DoctrineBundle@d6b3c37

[dominikzogg]

@beberlei as mentioned: there is code outside the symfony ecosystem out there

https://github.com/chubbyphp/chubbyphp-laminas-config-doctrine/pull/3/files and i am not even done yet => will lead to a major release on my side and when orm 3.0 gets released another major cause i am sure there will be (expected) bc's

[beberlei]

Adding any parameter could have caused this, others might use entity-manager instead of em. Not sure how this could have been prevented, we won't change this now. Sorry to cause extra work on your end.

[dominikzogg]

Not sure how this could have been prevented

do it in 3.0, so nobody get forced to update code immediately

[beberlei]

That ship has sailed :)