For using the API from a mobile device, first step is device registration. For doing this step, you should call this service.
After registration step and receiving api_key, you need to call this service to get a unique token and use it when calling other services.
When you call Login service and make an authenticated session to the server, dependent to your timeout value while log-in, you should call this service to renew your current session. for example if timeout value is 5 minutes, you should call this service every 5 minutes or less to renew your session. This service returns current tenant settings in response data.