Returns unblocked, manually selectable coaches and bookable seats.
Coaches without seats are omitted. The optional inventory-class filter
is applied to seats. Remote reservation errors retain the existing HTTP
200 envelope with error_code and error_message instead of coach data.
Returns unblocked, manually selectable coaches and bookable seats. Coaches without seats are omitted. The optional inventory-class filter is applied to seats. Remote reservation errors retain the existing HTTP 200 envelope with error_code and error_message instead of coach data.