Remove calls to #to_json in RelationsAPI

Rely instead on custom Formatter: see 0bf314f1

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Remove calls to #to_json in WorkPackagesAPI

Rely instead on custom Formatter: see 0bf314f1

Signed-off-by: Alex Coles <alex@alexbcoles.com>