add OSDU_GCP_REGISTER_URL with stub value

cloud-providers/osdu-gcp-cloudrun.yml

@@ -25,6 +25,8 @@
 .osdu-gcp-variables:
   variables:
     #services' urls
+    # placeholder(stub) for register service
+    OSDU_GCP_REGISTER_URL: https://os-register-dot-opendes.appspot.com/api/register/v1/
     OSDU_GCP_ENTITLEMENTS_URL: https://os-entitlements-gcp-attcrcktoa-uc.a.run.app/entitlements/v1/
     OSDU_GCP_AUTHORIZE_API: https://os-entitlements-gcp-attcrcktoa-uc.a.run.app/entitlements/v1/
     OSDU_GCP_STORAGE_URL: https://os-storage-dot-nice-etching-277309.uc.r.appspot.com/api/storage/v2/