parent task: https://phabricator.wikimedia.org/T339334

This ticket should only be picked up after https://phabricator.wikimedia.org/T344581 and https://phabricator.wikimedia.org/T344436 are done

In https://phabricator.wikimedia.org/T344436 we implement the discovery feature page layout without a real binding to our API endpoints and use mock-data and mock-endpoints instead.

ACs:

• UI is wired up to the actual API endpoints we built in https://phabricator.wikimedia.org/T344581