supertest Add cookie assertions framework

Add a convenient workflow for running assertions on cookie headers returned by the server. This code is largely copied from Gregory Langlais' package expect-cookies (MIT License).

Implements #855.

Example usage:

const request = require('supertest');
const cookies = request.cookies;

request(app)
  .get('/users')
  .expect('Content-Type', /json/)
  .expect('Content-Length', '15')
  .expect(200)
  // assert 'alpha' cookie is set with domain, path, and httpOnly options
  .expect(cookies.set({ name: 'alpha', options: ['domain', 'path', 'httponly'] }))
  // assert 'bravo' cookie is NOT set
  .expect(cookies.not('set', { name: 'bravo' }))
  .end(function(err, res) {
    if (err) {
      throw err;
    }
  });

Supports:

.set - Assert that cookie and options are set.
.reset - Assert that cookie is set and was already set (in request headers).
.new - Assert that cookie is set and was NOT already set (NOT in request headers).
.renew - Assert that cookie is set with a strictly greater expires or max-age than the given value.
.contain - Assert that cookie is set with value and contains options.
.not - Call any cookies assertion method with "assert true" modifier set to false.

Checklist

[x] I have ensured my pull request is not behind the main or master branch of the original repository.
[x] I have rebased all commits where necessary so that reviewing this pull request can be done without having to merge it first.
[x] I have written a commit message that passes commitlint linting.
[x] I have ensured that my code changes pass linting tests.
[x] I have ensured that my code changes pass unit tests.
[x] I have described my pull request and the reasons for code changes along with context if necessary.