GeoIP lookups used by delivery metrics.
These wrap the MaxMind (:locus) databases so they can be replaced by a stub in the test environment, avoiding any MaxMind database download.
:locus
@spec asn_info(String.t()) :: %{organization: String.t(), asn: integer() | nil}
@spec country_code(String.t()) :: String.t()
@spec geohash(String.t()) :: String.t()