We want to give feedback to the user as soon as possible about the
validity of the config supplied for the services.
When extending a service, we can validate that the fields are
correct against our schema but we must wait until the *end* of
the extends cycle once all of the extended dicts have been merged
into the service dict, to perform the final validation check on the
config to ensure it is a complete valid service.
Doing this before that had happened resulted in false reports of
invalid config, as common config when split out, by itself, is not
a valid service but *is* valid config to be included.
Signed-off-by: Mazz Mosley <mazz@houseofmnowster.com>
950577d60f