Locally run Cognito during tests

[hei-teacher]

Commit https://github.com/hei-school/hei-admin-api/commit/74166d4145451f3086804bb23d3f171485b44355 uses the Cognito emulator from https://github.com/jagregory/cognito-local. Unfortunately, that emulator does not support AdminInitiateAuth which makes it impossible to get authentication token. Keep an eye on that project, they might eventually implement that feature.

Alternately, Localstack provides support for Cognito. However, they do so in the Pro version only https://localstack.cloud/features/.