fix(server): print extra config keys on error (#5036)

server/src/domain/system-config/system-config.core.ts

@@ -328,7 +328,7 @@ export class SystemConfigCore {
         }
 
         if (!_.isEmpty(file)) {
-          throw new Error(`Unknown keys found: ${file}`);
+          throw new Error(`Unknown keys found: ${JSON.stringify(file)}`);
         }
 
         this.configCache = overrides;