code: @Nonnull
    public FineUploader5Session setEndpoint (@Nullable final ISimpleURL aEndpoint)
    {
      ValueEnforcer.notNull (aEndpoint, "Endpoint");
      m_aSessionEndpoint = aEndpoint;
      return this;
    }
docs: If non-null, Fine Uploader will send a GET request on startup to this
  endpoint, expecting a JSON response containing data about the initial file
  list to populate.
  
  @param aEndpoint
  New value. May be <code>null</code>.
  @return this for chaining