fix: define base policy for email sender

Author: sgtoj

assets/custom-email-sender/Dockerfile

@@ -16,6 +16,7 @@ RUN if [ "$APP_VERSION" != "latest" ] ; then git checkout $APP_VERSION ; fi
 RUN go mod download
 RUN go build -o bootstrap
 
+ARG SERVICE_OPA_POLICY_ENCODED=cGFja2FnZSBjb2duaXRvX2N1c3RvbV9zZW5kZXJfZW1haWxfcG9saWN5CnJlc3VsdCA6PSB7CgkiYWN0aW9uIjogImJsb2NrIiwKCSJibG9jayI6IHsKCQkibWVzc2FnZSI6ICJwb2xpY3kgd2FzIG5vdCBkZWZpbmVkIgoJfSwKfQo=
 RUN echo "$SERVICE_OPA_POLICY_ENCODED" | base64 -d > /opt/app/policy.rego
 
 # ------------------------------------------------------------------ package ---