Create API unittests with Docker Compose

The MLX API code relies extensively on _"deployed infrastructure"_ like the MySQL database and Minio S3 storage provisioned by Kubeflow Pipelines. Thus it is nearly impossible to test any of the API endpoints in isolation on a local developer notebook.

Since we now have a working MLX Katalog "deployment" with the [Quickstart guide](https://github.com/machine-learning-exchange/mlx/tree/main/quickstart) we should be able to implement a `unittest` suite for all of the Katalog specific API endpoints that do not rely on running Kubeflow Pipelines, like register, list, delete, download.

Once we have a working KIND (Kubernetes in Docker) setup #73 we should be able to point the `unittest` suite to that, or, to any provisioned MLX Kubernetes cluster.