Opa should always renew its IDP information

[daisieh]

In case the underlying Keycloak instance changes and therefore our saved IdP keys are invalidated, we need to make sure that we can update the value in Opa's vault store.

The authx change allows for us to call authx.auth.add_provider_to_opa again with our bearer token and update the value in vault any time the file /app/bearer.txt is found on startup.

To test: get a site admin token and save it to a file test.txt. Then run

docker cp test.txt candigv2_opa-runner_1:/app/bearer.txt
docker restart candigv2_opa-runner_1

You should see a log message Updating our IDP with a new bearer token at the time you did that. You should NOT see a message following that says IDP is incorrect: verify that Keycloak is set up and clean/build/compose opa again.