Add attributes_to_get parameter to Model.scan

[ButtaKnife]

Add the attributes_to_get parameter to Model.scan to enable projection expressions on scan operations.

[akashg90]

Is there any plan to release this change?

[ikonst]

@garrettheel lgtm, agree?

[garrettheel]

Ideally we'd add support for ProjectionExpressions, as AttributesToGet is now deprecated, but this is fine in the interim.

Can you please rebase and also update the stubs in the .pyi files (indexes.pyi and models.pyi)? [example]

[ButtaKnife]

(Posting this time with the correct account...)
Oh hey, I had not seen the most recent replies on this PR since it's so ancient. I was just pulling in the latest changes, but I'll do a rebase and see about addressing the stubs. It would be great if this could be merged soon.

Also, @garrettheel - agreed about ProjectionExpressions vs AttributesToGet, but I wasn't quite comfortable enough with the PynamoDB codebase to make that type of refactor yet.

[garrettheel]

Sorry for the delay @ButtaKnife. Would you mind resolving the conflicts and pinging me again so we can get this in?

[ButtaKnife]

@garrettheel - Merged the latest! We've been using these changes against a fairly recent version of master in microservices at work and it's been good so far. Would be amazing to get the PR merged in here so we can stop using my fork. :)

[garrettheel]

Thanks again!