Rename the release metadata key from current to last so it describes the
version it stores more accurately.
The value represents the most recent completed Docker release, while
next continues to track the upcoming release.
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
Add validation to ensure PRs have milestones set and that they match the
expected docker next version defined in releases configuration.
This prevents PRs from being merged without proper milestone tracking,
which is important for release management and ensuring changes are
properly categorized for upcoming releases.
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
