package spec validation of changelog changes.link field is ineffective

[efd6]

The validation for the changelog changes.link field requires that the pull request link be a positive integer. This check is performed during an elastic-package build run, erroring and refusing to complete when this is not the case. The consequence of this is that during package development a spec-valid placeholder must be put in place to allow the build to complete. The social consequence of this is that this valid placeholder can be forgotten during development and review, resulting in the semantically invalid, but syntactically valid value in the field. Thus the check is ineffective.

The elastic-package check subcommand also checks this (as an implementation detail, the way this happens is by calling build where the check ultimately happens, so disentangling them is less simple than it could be). Since this command is not required to build a package, but is run in CI, putting the validation checks in this subcommand and not in the build subcommand would ensure that the validations are not missed during CI and are not intentionally circumvented by devs in order to get a build to work.