afterResponse = (res) => {
    this.updateLimits(res.headers['x-shopify-shop-api-call-limit']);
    return res;
  }
Sends a request to a Shopify API endpoint.

@param {Object} uri URL object
@param {String} method HTTP method
@param {(String|undefined)} key Key name to use for req/res body
@param {(Object|undefined)} data Request body
@param {(Object|undefined)} headers Extra headers
@return {Promise}
@private