What changed

Containerises the API test suite and updates the STS mock push-to-main.yml action to build/tag/publish the test image to Dev and Build.

Why did it change

This partially implements the Testing step in the Secure Pipeline methodology, whereby automated tests are run and are used to determine whether to promote the application to the next environment. The other part of the implementation will be done in the https://github.com/govuk-one-login/mobile-id-check-async-infra repository (updating the secure pipeline and test image repository Cloudformation stacks).

This is a mock asset that isn't promoted to Production; however, it is still good to run these tests so that we are alerted in case there are issues in Dev or Build that we need to address.

This also introduces a new pattern for the team - Github reusable workflows (https://docs.github.com/en/actions/sharing-automations/reusing-workflows). The intent here is to create re-usable abstracted assets helping with maintainability and improves speed of adoption for new applications. This has only been done for functionality that builds/pushes/tags the docker image used in the test containers (AWS CodeBuild)

Testing

Action successfully runs for the Dev environment. It fails for Build due to IAM policy restrictions (only the main branch can push assets to Build`; this is expected.

run-tests-locally.sh passes, when run against the mob-sts-mock stack

Checklists

• There is a ticket raised for this PR that is present in the branch name
• No PII data logged. See guidance here
• Demo to a BA, TA, and the team.
• Update README with any new instructions or tasks