Enhancement: UMAPI_MOCK environment variable
The new environment variable UMAPI_MOCK
controls whether the umapi_client can be used with a mock server: either a proxy
server which accepts http and relays requests to the actual server via https, recording requests and responses; or a playback
server which accepts http, doesn't require auth, and simply plays back the server answers from a prior run. Both these modes are used by the user_sync test_framework.