Pull-through image cache

[martinohmann]

If my house is disconnected from the internet i'd like to still have access to the container images I use within my clusters. Spegel will mirror them within the main cluster, but the storage cluster does not benefit from this.

At work we use harbor proxy cache + pod-image-swap-webhook but i'd like to find a solution that does not need both:

• harbor is quite heavy, maybe zot is an alternative?
• pod-image-swap-webhook is a webhook that patches every pod. Maybe there's a more transparent solution here via containerd config?