Consider showing updated_at field in the container registry UI

Context

Currently on the Container Registry UI, we show the build timestamp.

What is the build timestamp?

When an image is built with e.g. docker build, the container runtime (Docker in this case) will compute a timestamp and embed it on the image. This is the timestamp that Rails treats as the tag creation timestamp. This is misleading (an image can be built now and only tagged several days after, so in that case, the shown timestamp is several days behind the actual tag creation date...), but there was really no other way of doing it so far due to the registries (our old registry and most of the current registries out there).

source

Screen_Shot_2022-08-22_at_12.51.53

On ~SaaS we could consider showing a different field that might be more useful for the customer:

  • The created_at timestamp of a tag is set once when the tag is first created on the registry side;
  • The updated_at timestamp of a tag is not set when the tag is first created on the registry side. Instead, it's set every time the tag is re-pushed.

To do

  • Determine if showing one of those fields would be a better user experience
  • Understand implications that SaaS and self-managed customers will have a different experience

More context: #351031 (comment 1055388147)