setup.sh does not support Oauth S2S

### Subject of the issue
As per title, the setup.sh script only supports JWT tokens and not OAUTH S2S. Needs updated to allow for OAUTH S2S service accounts to be used.

### Your environment
Latest

### Steps to reproduce
Run through setup.sh using an OAUTH S2S service account. JWT will be blank and token retrieval will fail.

### Expected behaviour
OAUTH S2S service accounts can be used with the setup.sh script and a token is successfully obtained

### Actual behaviour
400 error occurs due to wrong params.

Start by reading setup.sh and reproduce the failure using an OAUTH S2S service account. Compare the existing JWT token retrieval parameters with the requirements for OAUTH S2S, then rerun setup.sh to verify that a token is obtained without the 400 error.

Written by the indexing model from the issue text.