# When performing a redirect, this callback will be executed first. If the callback
    # returns true, then the redirect is followed, otherwise it is not. The request that
    # triggered the redirect and the response will be passed into the block. This can be
    # used to update any links on the client side.
    #
    # Example:
    #
    #   author_resource.on_redirect do |req, resp|
    #     post.author_uri = resp.header['Location']
    #   end
    #
    # @block callback<request, response>
    #   The action to be executed when a request results in a redirect. Yields the
    #   current request and result objects to the callback.
    def on_redirect(&callback)
      if block_given?
        @on_redirect = callback
      else
        @on_redirect
      end
    end