Add default values for route_short_name and route_long_name

[stefanw]

They are only 'conditionally required'.

Determining the 'requiredness' seems more a validation question and cannot be determined during deserialization.

Alternatively, they could be Option<String>s which is a more correct representation when the column is missing, but makes user code more complicated.

[antoine-de]

oups, forgot to reply to this, sorry :pray:

I feel we could enforce a bit more stuff on the type level here, but maybe you're right and it's overkill. I think we'll add a warning on the validator to enforce this :+1:

Thanks a lot!