Make SonataEasyExtends optional

[jordisala1991]

Subject

I am targeting this branch, because this is BC.

Part of: sonata-project/dev-kit#750

SonataEasyExtends is deprecated but it is used on many bundles, this makes it optional. This change is BC because if the user does not change anything it will continue using the deprecated code but with a message.

Changelog

### Changed
- SonataEasyExtendsBundle is now optional, using SonataDoctrineBundle is preferred
### Deprecated
- Using SonataEasyExtendsBundle to add Doctrine mapping information

To do

• Update the documentation;
• Add an upgrade note.

[greg0ire]

Why the huge drop in coverage?

[jordisala1991]

the extension is not tested, I will try to add some test, those PR will be huge. I saw the recipes from flex and contain the Orm relations, so I will need to change them too, and create the missing ones.

[greg0ire]

🤔 so is that PR finished or do you plan to do this later?

[jordisala1991]

It is not finished, I will change it to draft again. And it cannot be merged if the bug on extensions is not merged.

[jordisala1991]

Why the huge drop in coverage?

The drop in coverage is due to not testing the deprecated easy extends code

[jordisala1991]

Blocked by: #173 too

[SonataCI]

Could you please rebase your PR and fix merge conflicts?

[greg0ire]

We should try to remember this while releasing. Would be great to have a keyword and have the release tool warn us that we need to do something.

Awaiting clarification on #171 (comment)

[greg0ire]

Thanks @jordisala1991 !

[phansys]

IMO, this section must be updated in order to show the remaining persistence bundles.

[jordisala1991]

I left only the implemented ones for the ArticleBundle