Image references passed to a CNB builder are not validated

[scottfrederick]

See #21483 for an example of a user providing an image name that causes a failure in the CNB builder that is difficult to diagnose (upper-case characters in the image name):

[INFO]  > Running creator
[INFO]     [creator]     ERROR: failed to all tags must have the same registry as the exported image: could not parse reference: docker.io/library/SchedulePolling:1.2

If we better understood the rules for an image reference, Boot could do some validation of the image name before invoking the builder to give a better user experience. For comparison, the pack CLI gives a more concise error message, although still missing the details of what isn't acceptable about the image name:

$ pack build docker.io/library/DemoProject:1.0 --builder gcr.io/paketo-buildpacks/builder:base-platform-api-0.3 --path build/libs/demo-0.0.1-SNAPSHOT.jar
ERROR: invalid image name 'docker.io/library/DemoProject:1.0': could not parse reference: docker.io/library/DemoProject:1.0

[scottfrederick]

For reference, the Google go-containerregistry library contains some rules for elements of the image name:

• Characters allowed in repository element
• Characters allowed in tag element
• Characters allowed in digest element