def to_param
      params = to_hash.merge(
        'callerKey' => AmazonFlexPay.access_key,
        'signatureVersion' => 2,
        'signatureMethod' => 'HmacSHA256'
      )
      params['signature'] = AmazonFlexPay.sign(AmazonFlexPay.pipeline_endpoint, params)
      AmazonFlexPay::Util.query_string(params)
    end
def to_param
      params = to_hash.merge(
        'callerKey' => AmazonFlexPay.access_key,
        'signatureVersion' => 2,
        'signatureMethod' => 'HmacSHA256'
      )
      params['signature'] = AmazonFlexPay.sign(AmazonFlexPay.pipeline_endpoint, params)
      AmazonFlexPay::Util.query_string(params)
    end
Converts the Pipeline object into parameters and signs them.