Add the address of Signer to the policy service config

env/policy.env

@@ -11,4 +11,5 @@ MONGO_DBNAME="policy"
 MONGO_COLLECTION="policies"
 CACHE_ADDR="http://cache:8080"
 TASK_ADDR="http://task:8080"
+SIGNER_ADDR="http://signer:8080"
 DID_RESOLVER_ADDR="http://didresolver:8080"