code: @Nonnull
    public FineUploaderBasic addParam (@Nonnull @Nonempty final String sKey, @Nonnull final String sValue)
    {
      ValueEnforcer.notEmpty (sKey, "Key");
      ValueEnforcer.notNull (sValue, "Value");
  
      m_aRequestParams.put (sKey, sValue);
      return this;
    }
docs: These parameters are sent with the request to the endpoint specified in the
  action option.
  
  @param sKey
  Parameter name
  @param sValue
  Parameter value
  @return this