As mentioned on https://bitbucket.org/metabrainz/musicbrainz-server/pull-request/544/mbs-6832-format-coordinates-for-display/diff coordinates are currently modeled such that there is always a coordinates object, but sometimes latitude and longitude are null; at a database level it's either the whole coordinates are null or both are set, which would be more accurately modeled in Perl as a nullable coordinates object with required/not-nullable latitude and longitude properties.

This would additionally simplify Entity::Coordinates->format and ->osm_url, which currently have to check for nulls.