introduce /images/json?containers=true parameter

[ndeloof]

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close #43244

- What I did
Restored the ability to list number of containers using an image with /images/json API

- How I did it
introduced new parameter containers to trigger (pre-existing) counting logic

- How to verify it
curl http://localhost:2375/v1.41/images/json?containers=true | jq

- Description for the changelog
GET /images/json now accepts query parameters containers to count containers using each image

[thaJeztah]

I think the reason that field was not filled was because this field was added specifically for the /system/df endpoint. When that was added, the same struct was re-used (yeah..), but the field left empty (or set to -1). b308097 (#42550) added some extra comment elsewhere in the code, but may need more details there.

We should look how useful it is to add this information to docker image ls (which uses this endpoint), and check if there's no possible side-effects of adding it here (although I think the container count comes from the memory-store, so probably won't cause much overhead (famous last words)).

The main issue in , however, looks to be due to the ImageSummary being completely un-documented in the swagger file,

moby/api/types/image_summary.go

Line 8 in 7b9275c

type ImageSummary struct {

, so it gives no clue whatsoever what each fields is (and when it's used); that's definitely something we should fix (probably we can copy some docs that were added in #43300)

[thaJeztah]

oh! there's a typo in your commit message (conainers - missing a t)

[ndeloof]

I think the container count comes from the memory-store, so probably won't cause much overhead

ImageService comptes this value by filtering on containers.List(), and the container store it is configured with is container.NewMemoryStore(), so this seems to be fine