def flat_prefs
      separator = id ? "/" : "_"
      attributes[:prefs].inject({}) do |hash, (pref, v)|
        hash.merge("prefs#{separator}#{pref}" => v)
      end
    end
def flat_prefs
      separator = id ? "/" : "_"
      attributes[:prefs].inject({}) do |hash, (pref, v)|
        hash.merge("prefs#{separator}#{pref}" => v)
      end
    end
On creation
 https://trello.com/docs/api/board/#post-1-boards
 - permissionLevel
 - voting
 - comments
 - invitations
 - selfJoin
 - cardCovers
 - background
 - cardAging

 On update
 https://trello.com/docs/api/board/#put-1-boards-board-id
 Same as above plus:
 - calendarFeedEnabled