Backport boilerplate changes (Login and Consent Webapp)

Backport boilerplate changes to the Login and Consent Webapp repository. This includes (where relevant):

• implement poetry for dependency management
• use of poetry poe to execute scripts
• run tests (tox) via poetry poe
• update any relevant pipeline checks
• setup pre-commit checks
• deploy latest master to relevant environments

Part of uis/devops/webapp-boilerplate#114