Support PRs to use PR ID in the docker images pushed to our docker registry

[mdelapenya]

When packaging a PR, the generated docker image is pushed to our docker registry with the name of the snapshot. We'd like to generate the docker image including the PR ID:

- def newName = "${DOCKER_REGISTRY}/observability-ci/${name}:${libbetaVer}"
- def commitName = "${DOCKER_REGISTRY}/observability-ci/${name}:${env.GIT_BASE_COMMIT}"
+ def newName = "${DOCKER_REGISTRY}/observability-ci/${name}:${PR_ID}-${libbetaVer}"
+ def commitName = "${DOCKER_REGISTRY}/observability-ci/${name}:${PR_ID}-${env.GIT_BASE_COMMIT}"

cc/ @elastic/observablt-robots @ph @EricDavisX

[mdelapenya]

I'm thinking about the proposed name, and I could see two different choices:

1. def newName = "${DOCKER_REGISTRY}/observability-ci/${name}:${libbetaVer}"
2. def newName = "${DOCKER_REGISTRY}/observability-ci/${name}/${PR_ID}:${libbetaVer}"

The first one adds the PR-ID to the tag, and the second one adds it to the namespace. I like the second one as it preserves the tag name structure, so it's easier to identify the tag.

Which one do you prefer?

[ph]

I like option 2.

[mdelapenya]

Adding @kuisathaverat's comments for context: #20323 (comment)

[mdelapenya]

What he suggests is a third option:

3. def newName = "${DOCKER_REGISTRY}/observability-ci/${name}:${PR_ID}

I like this option the most