Add onReference event when a new lazy object reference is created

[GromNaN]

Q	A
Type	feature
BC Break	no
Fixed issues	Fix #2916

Summary

This feature enable the injection of dependencies into lazy documents, even if they are not loaded.

I am willing to discuss whether this feature is a good idea.

[alcaeus]

This feature enable the injection of dependencies into lazy documents, even if they are not loaded.

I am willing to discuss whether this feature is a good idea.

I'm not opposed to the idea of such an event, but I think that injecting dependencies into lazy documents isn't it. Lazy documents are supposed to be transparent, which we're now achieving better than before by using native PHP functionality. Note that this wouldn't work if the document isn't lazy-loaded, so this would always have to be used alongside a PostLoad event for it to work properly in all scenarios.