code: @Nonnull
    public AS2ClientBuilder setContentTransferEncoding (@Nonnull final EContentTransferEncoding eCTE)
    {
      ValueEnforcer.notNull (eCTE, "ContentTransferEncoding");
      m_eCTE = eCTE;
      return this;
    }
docs: Set a custom <code>Content-Transfer-Encoding</code> type. By default the
  AS2-default 'binary' is used. This setting alters the way how the payload
  is encoded inside the transmitted AS2 message and must usually not be set!
  
  @param eCTE
  The new content transfer encoding to be used. May not be
  <code>null</code>.
  @return this for chaining
  @since 2.0.7