Sorry for not providing a clear direct answer here, but this video helped me a lot to get up and running with Workload Identity Federation, so I'll definitely recommend watching this:
https://youtu.be/AH5DmYsKSTM?si=CXURPYcMIWyQx1iS
(He provides a script that automatically sets up everything you need to run terraform from github actions workflows)
https://github.com/amir-cloud-security/gcp-terraform-test-oidc