chore : integrate ssr test + broken link checker to CI

[jeffcorpuz]

Resolves #456
Impact: minor
Type: test

Issue

• SSR integration test was failing via CI, not locally.
• Broken link checker was turned off due to flaky environments

Solution

Due to SSR need to be rendered on a browser, it needed a way to test it out.

A solution was to add the SSR / integration step as a dependency on the ecs-deploy job in CI with an accompanying staging url environment call. Similar to how future e2e tests will run.

To make sure it can be tested for local development, add a ternary conditional operation that defaults to localhost:4000 if no env variable is set.

Due to the stability of the staging environment, re-activate the broken link checker.

Runs as a dependency for the ecs-deploy job in CI.

Testing

1. After successful merge to deploy, validate if tests run in CI
2. Validate able to run locally without declaration of the URL variable and default runs via localhost on starter-kit

Example CI output : https://circleci.com/gh/reactioncommerce/reaction-next-starterkit/7376

[griggheo]

Looks good to me.