Make SelectExpandBinder public and register it in RequestContainer (the same way as FilterBinder)

[savelievser]

FilterBinder is a good example of class that is open for expanding. I can derive from it and override some methods. Then I can register my class in container, so i will be used instead of original FilterBinder. But I can't do the same with SelectExpandBinder. I would be great to refactor it in the same way and make public.

[xuzhg]

@savelievser Would you please contribute it? we'd happy to review and merge it.

[savelievser]

@xuzhg sure

[dropsonic]

@xuzhg any updates on this feature and the corresponding PR? It's been a year since the PR was created.