swagger-ui/test/e2e-cypress/static/documents/features/response-extension.swagger.yaml

swagger: "2.0"

paths:
  /:
    get:
      operationId: "myOperation"
      tags: ["myTag"]
      summary: an operation
      responses:
        "200":
          description: ok
        '404':
          x-error: true
          x-error-codes: [NOT_FOUND]
          description: Not found