Expose expert consultants via pathways (#180).

[napakalas]

This update adds expert-consultants to pathways so it can be accessed from the flatmap server.

[dbrnz]

When looking at similar code in pathways.py, my editor shows various warnings associated with types. It would be prudent to resolve these by adding type annotations and default values as needed. Thanks.

[napakalas]

Thanks for the suggestion. I’ve updated several lines to resolve the type-related warnings by adding appropriate type annotations and default values.