Use a request property instead of global var for tenantId

[pjoe]

In Lab2/Part3 a global var is used to store tenantId for incoming requests. Not sure how that would work with multiple requests in flight.

aws-saas-factory-bootcamp/Lab2/Part3/product-manager/server.js

Lines 22 to 36 in b530405

	var tenantId = '';
	// Configure middleware
	app.use(bodyParser.json());
	app.use(bodyParser.urlencoded({extended: false}));
	app.use(function(req, res, next) {
	res.header("Access-Control-Allow-Origin", "*");
	res.header("Access-Control-Allow-Methods", "GET, POST, OPTIONS, PUT, PATCH, DELETE");
	res.header("Access-Control-Allow-Headers", "Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With");
	bearerToken = req.get('Authorization');
	if (bearerToken) {
	tenantId = tokenManager.getTenantId(req);
	}
	next();
	});

A better way would be to store this on the request object, see example: https://expressjs.com/en/guide/writing-middleware.html (under "Middleware function requestTime")

[brtrvn]

NodeJS is a single threaded system - so every request gets lives in its own scope. There wouldn't be a way to leak across requests. That said, if it makes more sense to pass the tenant id through mutating the incoming request object, there's no harm that I can see.