HAFAS(3pm): get_service: Document coverage and homepage keys

=over

=item B<name> => I<string>

=item B<coverage> => I<hashref>

service name, e.g. Bay Area Rapid Transit or Deutsche Bahn.

Area in which the service provides near-optimal coverage. Typically, this means

a (nearly) complete list of departures and real-time data. The hashref contains

two optional keys: B<area> (GeoJSON) and B<regions> (list of strings, e.g. "DE"

or "CH-BE").

=item B<mgate> => I<string>

=item B<homepage> => I<string>

HAFAS backend URL

Homepage URL of the service provider.

=item B<languages> => I<arrayref>

Languages supported by the backend; see the constructor's B<language> argument.

=item B<name> => I<string>

Service name, e.g. Bay Area Rapid Transit or Deutsche Bahn.

=item B<mgate> => I<string>

HAFAS backend URL

=item B<productbits> => I<arrayref>

MOT bits supported by the backend. I<arrayref> contains either strings