code: public String getVaultClass() throws Exception {
          Address addr = Address.root().add(CORE_SERVICE, VAULT);
  
          ModelNode vaultNode = readResource(addr);
          if (vaultNode == null) {
              return null;
          }
  
          ModelNode codeNode = vaultNode.get("code");
          if (codeNode == null) {
              return null;
          }
  
          return codeNode.asString();
      }
docs: Attempts to retrieve the configured class for the vault. This method will
  return null if no vault is configured or if the vault does not have a custom
  vault class.
  
  @return vault configured class
  @throws Exception any error