[WIP] OP-2695 Use Mobile device location services (lat/lng) to return local deals for users

Add active_from_lat_lng and from_lat_lng methods to the region model.

The homerun PR related to this is: https://github.com/demandchain/homerun/pull/3397

Will add tests if this looks good to reviewers.  I've tested in rails console, and the methods indeed return a region.