Properties listed in `required` should be declared in `properties`

[gregsdennis]

This is implemented by AJV's strict mode.

Comments

I feel there are legitimate times when this is desired (e.g. inside an if/then/else or oneOf). Usually a parent schema can declare properties but the subschemas would only control which properties are required. - @gregsdennis

I don't thing we should do this one. The only way this would make sense is if you could analyze the whole schema (including external references) to determine if the property isn't declared in any sub-schema that applies to a location. To the best of my knowledge, that's way outside the capabilities of Spectral. - @jdesrosiers