Investigate: are the Nextclade CLI containers that Cladetime pulls from Docker cached?

[bsweger]

Background

On April 1st, Docker is updating its pull rate limits as follows for free personal users:

Unauthenticated users: 10 pulls/hour
Authenticated users with a free account: 100 pulls/hour

Cladetime pulls the Nextclade CLI image from Docker to use for getting Nextclade datasets and doing clade assignments: https://github.com/reichlab/cladetime/blob/main/src/cladetime/util/reference.py#L97

Definition of done

• Better understand if/how the Python Docker client used by Cladetime caches the downloaded image
• If needed, create a follow-up issue to ensure that Cladetime users don't hit the new rate limits