This diff introduces a function to build a Tonic client for further API calls in integrational tests. The pointer to the client will be passed to the helper functions (in D5931) instead of making the "global" client instance.
We are using COMM_SERVICES_PORT_TUNNELBROKER environment variable to provide a port to connect to the Tunnelbroker.
The COMM_SERVICES_HOST_TUNNELBROKER environment variable provides a host to connect to the Tunnelbroker.
Linear task: ENG-1657