Modify the service update and create APIs to return optional warning
messages as part of the response. Populate these messages with an
informative reason when digest resolution fails.
This is a small API change, but significantly improves the UX. The user
can now get immediate feedback when they've specified a nonexistent
image or unreachable registry.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
(cherry picked from commit 948e60691e)
Signed-off-by: Victor Vieux <victorvieux@gmail.com>
