Trouble with client-secret.json

[mikgross]

Hi all,
quick question which is not really an issue:
Is the client-secret.json the key for the service account? If yes, why did we set up the key in the secret? Should it be used like so:

gcloud auth activate-service-account ${{ secrets.GCP_SA_EMAIL }} --key-file=${{ secrets.GCP_SA_KEY }}

I am having a bit of trouble to understand the doc here.