PROD-88182: fix add-visitor-id middleware to use ctx.origin correctly after koa v3 upgrade

[Michalis-Apostolou]

After upgrading to koa 3 there was a breaking change on ctx.origin.
https://github.com/koajs/koa/releases/tag/v3.0.0

req.origin should display the origin header if it exists, not the current hostname koajs/koa#1008. origin now aligns with the Origin header as used in CORS.

on add-visitor-id middleware we try to set the a cookie.

Instead of using ctx.origin to calculate the domain of the cookie , we use ctx.request.URL.origin as per discussion koajs/koa#1008 (comment)

Also changed the order on how the domain resolved. Previously we calculated the default way and then overwrite it with the callback provided.

Issue

If a request had an invalid origin header , it couldn't be parsed by new URL(ctx.origin) and it threw , resulting to 500 response.

[kkyriakidis]

Suggested change

	before(function() {
	before(function() {
	server.config.visitor.getCookieDomain = () => 'domain-provider-cb';
	});
	after(function() {
	delete server.config.visitor.getCookieDomain;
	});

to avoid leaking getCookieDomain
very minor as it is the last test in the file

[Michalis-Apostolou]

done

[kkyriakidis]

an invalid Origin header doesn't affect the request.URL which tehn parses from Host: localhost:3220
maybe we rename this test to

Suggested change

	describe('when origin header is invalid', function() {
	describe('when the Origin header is malformed', function() {

we can also add a test for a valid but foreign origin

Suggested change

	describe('when origin header is invalid', function() {
	describe('when the Origin header is a different origin', function() {
	it('derives the cookie domain from the host, not from Origin', async () => {
	const response = await supertest('localhost:3220')
	.get('/test')
	.set('origin', 'https://evil.example.com')
	.expect(200);
	const visitorCookie = response.headers['set-cookie'].find(c => c.startsWith('wmc='));
	should(visitorCookie).not.be.undefined();
	visitorCookie.should.match(/domain=localhost/i);
	visitorCookie.should.not.match(/evil\.example\.com/i);
	});
	});

[Michalis-Apostolou]

done