Support for doctrine's orm embedded

[jennevdmeer]

Doctrine Embedded

This is a draft I have been sitting on for while using it in personal projects that could fix #866, which is a continuation/alternative suggestion for what was talked about in #350

For now I am looking for some feedback on my approach by people with a broader understanding of the bundle to check if this can move forward or there might be some blockers on the way since I only use the bundle for some basic image uploads.

How it's used

The general principle in both triggered from the listener (just Metadata/Driver/AnnotationDriver) and asset helper is that this traverses objects up towards the nearest non embeddable and use that as a property path. These can then be
used as e.g. vich_uploader_asset(promotion, 'images.banners.largeRectangle')

I made a small SF test project for this PR since my projects where I have used it aren't public at https://github.com/jennevdmeer/vich-uploader-embeddable-test

The entity/embeddables are not really anything new, the only thing to keep in mind is that the entity and the embeddables both need the Vich/Uploadable marking. See my test project entity. And the two embeddables; child, grandchild examples.

The form types (example) work as you would expect with nested objects and do not change.

What works

• (Recursive) embeddables
• Using it with symfony forms
  • The VichImageType and VichFileType form type
  • The delete/download functionality in the default form template
    
• SF profiler mapping collector
  

Known issues

• Each embeddable entity should have its own modified at to trigger the listener as is already the case and described on https://github.com/dustin10/VichUploaderBundle/blob/master/docs/usage.md#step-2-link-the-upload-mapping-to-an-entity / Upload is not performed if there is no change in the entity #297

  But since embeddables have no reference to its parent you can not change a property there from the setters in the embeddable classes.

Not looked at yet

• Other configuration methods other than Attributes;
• ODM Embedded (I only have MySQL set up and no other DB experience);
• if it works together with the #[ORM\Embedded(class: 'Vich\UploaderBundle\Entity\File')];
• any existing tests, or creating any new ones for this other than my basic sf demo project.