* 🐛 Dynamic Routing Beta: Shortform `author.foo` is not allowed
refs #9601
- otherwise you get access to {{author}} in the theme, which is deprecated & causes errors
- recommend not using {{author}} as data longform name in the yaml validator
- (internal usage is still allowed)
- also warn against using reserved data key names like filter, resource, limit etc - maybe remove this restriction later but seems like a sensible validation right now.