DIG-898: allow service_token to view user_key

[daisieh]

Specifically allow the service token to view the decoded user key.

To test: clean/docker-volumes/build/compose opa, then try calling

curl -X "POST" "http://candig.docker.internal:8181/v1/data/idp" \
     -H 'Content-Type: application/json' \
     -H 'Accept: application/json' \
     -H 'X-Opa: opa-service-token' \
     -d $'{
  "input": {
    "token": "user token"
  }
}'

You should get the value of the user key (the email) as a response.

[OrdiNeu]

Works as expected for a service token ✔️ I double checked the JWT manually as well