Create endpoint
Create Endpoints/Units/UnitsEndpoint.php, extend AbstractEndpoint, and
implement basePath(). Add a public operation returning a concrete response.
Use sendGet() for a GET request and sendPost(), sendPut(), or
sendDelete() for other operations. Pass responseClass and uri explicitly.
Use Options to serialize request bodies.
The endpoint guide contains a complete
UnitsEndpoint example. Then implement its
JSON response.