def execute
      request = Net::HTTP::Post.new(@endpoint_uri.path)
      add_headers(request)
      request.body = URI.encode_www_form(string_hash(params))
      TokenResponse.parse(http(@endpoint_uri).request(request).body)
    end
def execute
      request = Net::HTTP::Post.new(@endpoint_uri.path)
      add_headers(request)
      request.body = URI.encode_www_form(string_hash(params))
      TokenResponse.parse(http(@endpoint_uri).request(request).body)
    end
Requests and waits for a token from the endpoint.
 @return TokenResponse