Calls requiring authentication expect an HTTP header Authorization including either a token, or a username / password combination, in the following format:
A test account is available:
demotestF8CpmeDJ8yzqk8fejF0cG5Ls7renAuthorization: Bearer your_api_tokenor
Authorization: Token your_api_token
Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=
In this example, dXNlcm5hbWU6cGFzc3dvcmQ= corresponds to 'username:password' encoded in base64.
You can also use the username / password combination via -u cURL, or via auth Guzzle.