Mark classes as final

[franmomu]

Subject

Similar to sonata-project/SonataDoctrineORMAdminBundle#1127

I am targeting this branch, because these changes are BC.

Changelog

### Changed
- Mark some classes as final.

[VincentLanglet]

I didn't take attention to https://github.com/sonata-project/SonataDoctrineORMAdminBundle/pull/1127/files#diff-5932af620464f5fdaec84991e9c2f0faR43

But in my personal project I override the ModelManager,

• I override the getDataSourceIterator to use my own SourceIterator

And I think that someone could just want to override some config methods like

getDefaultSortValues
getDefaultPerPageOptions
...

How to do this if the ModelManager is final ?
cc @core23 (and @sonata-project/contributors), we may have to revert this final annotation.

[core23]

We decided that we make everything final by default unless someone give a good reason why they can't use service decoration.

We should decide it on an individual basis.

[VincentLanglet]

We decided that we make everything final by default unless someone give a good reason why they can't use service decoration.

We should decide it on an individual basis.

Yes, that's why I gave reasons. And I was looking for confirmation that it was good reasons ^^

[VincentLanglet]

Let's go with this. I'll make a new release after this merge.

[VincentLanglet]

Thanks @franmomu