code: private void validateTenantUpdate(TenantDefinition oldTenantDef,
                                        TenantDefinition newTenantDef) {
          Utils.require(oldTenantDef.getName().equals(newTenantDef.getName()),
                        "Tenant name cannot be changed: %s", newTenantDef.getName());
          Map<String, Object> oldDBServiceOpts = oldTenantDef.getOptionMap("DBService");
          String oldDBService = oldDBServiceOpts == null ? null : (String)oldDBServiceOpts.get("dbservice");
          Map<String, Object> newDBServiceOpts = newTenantDef.getOptionMap("DBService");
          String newDBService = newDBServiceOpts == null ? null : (String)newDBServiceOpts.get("dbservice");
          Utils.require((oldDBService == null && newDBService == null) || oldDBService.equals(newDBService),
                        "'DBService.dbservice' parameter cannot be changed: tenant=%s, previous=%s, new=%s",
                        newTenantDef.getName(), oldDBService, newDBService);
      }
docs: Validate that the given modifications are allowed; throw any transgressions found.