Validations for preferences should be done in concerns, not controller
Currently, the Preferences controller handles all validation. I should update it to only check to make sure values are not nil - everything else should be handled in a concern for the model, and I should store valid options for drop-down menus (default column, theme, date format) inside the Preferences model, with a helper method to get them from the controller and concern.
I might end up putting them in a helper file instead of the model, but either will be better than the current implementation with a large controller and slim model (when MVC principles dictate it should be the other way around).