Update __find_records_by_ids to implement Strategy per ORM.

[jeyb]

I haven't done much for the other ORMs as I am not too familiar with them. But this does give a good base to add customizations.

[jeyb]

@karmi whatcha think?

[karmi]

@jeyb Can you please remove the copy & paste from import code crumbs? :) Also, I think the test could be more readable?