User defined ordering function

[ogizanagi]

Hi there.

Many thanks for the amazing work on this library.

I wonder if a custom user defined ordering function might be useful ?
Concrete case: All my entities use a TimestampableTrait (very similar to the one provided by DoctrineExtensions), adding both createdAt and updatedAt fields. Those fields are declared with proper annotations in order to allow serialization. (VirtualProperty on a custom method or Expose directly on the trait properties).

As for readability, the traits use is declared at the top of my entities, without any defined order policy (ACCESSOR_ORDER_UNDEFINED), this results in the fact that created_at and updated_at fields are always before any other fields after serialization.

For this use case, the aim is to provide a way to use a custom ordering function, which will always put created_at and updated_at fields at the bottom.

I think there might be some other use cases.

What do you think ?

Note: I guess VirtualProperty are still ignored as mentioned in the #349. So, this will only work for properties for now.

[goetas]

Closing, Sorry for the long feedback loop.

This can be already solved with http://jmsyst.com/libs/serializer/master/reference/annotations#accessororder