code: public static void addResponseHeader (@Nonnull @Nonempty final String sName, @Nonnull @Nonempty final String sValue)
    {
      ValueEnforcer.notEmpty (sName, "Name");
      ValueEnforcer.notEmpty (sValue, "Value");
  
      s_aRWLock.writeLocked ( () -> s_aResponseHeaderMap.addHeader (sName, sValue));
    }
docs: Adds a response header to the response according to the passed name and
  value. If an existing header with the same is present, the value is added to
  the list so that the header is emitted more than once.
  
  @param sName
  Name of the header. May neither be <code>null</code> nor empty.
  @param sValue
  Value of the header. May neither be <code>null</code> nor empty.