code: public MockResponse addHeaderLenient(String name, Object value) {
      InternalKtKt.addHeaderLenient(headers, name, String.valueOf(value));
      return this;
    }
docs: Adds a new header with the name and value. This may be used to add multiple headers with the
  same name. Unlike {@link #addHeader(String, Object)} this does not validate the name and
  value.