Viewing entities at a version, without reverting in the database

[sneako]

Hi and thanks for the useful library!

I would like to allow my users to preview the entity before a specific version. It seems that currently one would have to use the revert/2 function on the Repo, but this would actually rollback the changes in the database as well.

Would you be open to accepting a PR that essentially breaks Queryable.revert/3 in half, extracting the first half in to a function like entity_at_version/3 (happy to discuss better names, maybe preview/3?). This function would simply return the result of Enum.reduce(versions, struct, &_revert/2), which is currently in Queryable.revert/3, without changing anything in the database. We could then expose this function as well, on the Repo.

Thoughts?

[narrowtux]

This information should be available in the history function, but yes, it should also be possible to preview a specific version id.