refactor(secrets): calculate key vault URL from runtime env

similar to how this is done in the Terraform module

benefits/secrets.py

@@ -1,17 +1,27 @@
 import sys
 
+from django.conf import settings
+
 from azure.identity import DefaultAzureCredential
 from azure.keyvault.secrets import SecretClient
 
 
+KEY_VAULT_URL = "https://kv-cdt-pub-calitp-{env}-001.vault.azure.net/"
+
+
 if __name__ == "__main__":
     args = sys.argv[1:]
-    if len(args) < 2:
-        print("Provide the Key Vault URL and the name of the secret to read")
+    if len(args) < 1:
+        print("Provide the name of the secret to read")
         exit(1)
 
-    vault_url = args[0]
-    secret_name = args[1]
+    # construct the KeyVault URL from the runtime environment
+    # see https://docs.calitp.org/benefits/deployment/infrastructure/#environments
+    # and https://github.com/cal-itp/benefits/blob/dev/terraform/key_vault.tf
+    runtime_env = settings.RUNTIME_ENVIRONMENT()
+    vault_url = KEY_VAULT_URL.format(env=runtime_env[0])
+
+    secret_name = args[0]
 
     credential = DefaultAzureCredential()
     client = SecretClient(vault_url=vault_url, credential=credential)