Feature/edit metadata authorization

I assume that pds_handle contain user group name(s) and thus we don't need to add roles. To reflect this I added customized method "groups" to user model. If the assumption is incorrect I will fix it and edit roles file.

@ekate Yeah so the `logged_in_users.yml` has the 2 separate users, however I'm perfectly happy for you to use other cassettes if that's too confusing. I was thinking one file could be used to add arbitrary users and only have to ever `use_cassette(logged in users)`. So one could be gis_cataloger, one fda_cataloger, one could have both roles if need be (i.e. FDA_GIS_Cataloger). But yeah with the iterations I see how this is a bit convoluted, I find VCR to be a bit confusing in general.