docs: @Nonnull
    public final UnifiedResponse addCookie (@Nonnull final Cookie aCookie)
    {
      ValueEnforcer.notNull (aCookie, "Cookie");
  
      final String sKey = aCookie.getName ();
      if (m_aCookies == null)
        m_aCookies = _createCookieMap ();
      else
      {
        if (m_bWarnOnDuplicateCookies && m_aCookies.containsKey (sKey))
          logWarn ("Overwriting cookie '" + sKey + "' with the new value '" + aCookie.getValue () + "'");
      }
      m_aCookies.put (sKey, aCookie);
      return this;
    }