The generator pulls column names and types from the database,
using the methods `.type_for_attribute` and `.reflections`.

- Fill in missing mappings to `BaseDashboard#field_registry`.

References:
http://edgeguides.rubyonrails.org/generators.html
https://github.com/ryanb/nifty-generators

https://trello.com/c/My9ldlzZ