Document how to interact with Magento2’s REST API

[real34]

Gather documentation from our old tools, and update this issue with relevant documentation information before adding them to official developers documentation.

Goal: allow developers to interact with exposed REST API from Magento2 modules

---

Here are some notes:

• When M2.3 will have been integrated (and if it seems relevant) recommend to implement a GraphQL API directly so it could be proxied directly (+ write another documentation page to explain how)
• Fallbacks when logged out (to refresh a token)
• scopes (Magento)
• admin API (integration)

// src/server/model/magento2Connector/factories.js
module.exports = {
  makeUserClientFromRequest,
  makeAdminClientFromRequest,
  makeAuthServiceFromRequest,
  makeSearchDataSourceFromRequest,
  makeCartUrlBuilderFromRequest,
  makeStoreConfigFromRequest
};

const {
  makeUserClientFromRequest,
  makeAuthServiceFromRequest
} = require("../magento2Connector/factories");

    const axiosInstance = makeUserClientFromRequest(
      config.magentoEndpoint,
      req
    );
    const authService = makeAuthServiceFromRequest(req);

[real34]

cartUrlBuilder: see https://front-commerce.slack.com/archives/C929PBHUZ/p1556019299007500

    const cartUrlBuilder = makeCartUrlBuilderFromRequest(
      config.magentoEndpoint,
      req
    );
    cartUrlBuilder.fetchCart().toPromise().then(cart => ...);
    // ou
   cartUrlBuilder.cartId().toPromise().then(id => ...);