Add Minio to backend compose stack & CI

[spwoodcock]

• Decided on Minio over Garage - it's has better assurances of maintained, and is time tested.
• Add Minio to docker-compose stack in development (+staging).
• Minio is not required in production - we use managed S3 buckets instead.

[robsavoye]

Will this then only work with S3 ? I still need to be able to run everything locally.

[spwoodcock]

You will have to run with the docker compose stack going forward, or run your own Minio instance (which is easy) and connect to that.

I will add docs for both 👍

By locally you mean without docker right?
As this will run locally without issues (minio runs locally).
In production we will use managed S3 on AWS.