Challenge 3: Versioned Routes — Solution

# config/routes.rb
namespace :api do
  namespace :v1 do
    resources :comments
  end
end

# generates: /api/v1/comments, /api/v1/comments/:id, ...

# app/controllers/api/v1/comments_controller.rb
module Api
  module V1
    class CommentsController < ApplicationController
      # ...
    end
  end
end

=begin
Notes:
- Each namespace call adds one segment to both the URL path and the
  expected module nesting for the controller -- namespace :api then
  namespace :v1 together produce the /api/v1/... path prefix and require
  the controller to live at Api::V1::CommentsController, matching Rails'
  path-mirrors-module-structure convention.
- resources :comments inside the nested namespace still generates all 7
  RESTful routes from rails1-2, just under the versioned prefix -- nothing
  about the route-generation behavior itself changes.
- The module Api / module V1 nesting in the controller file is required to
  match the namespace declaration exactly; a class defined as plain
  CommentsController in that file would not be found by the versioned
  route.
- Adding a v2 namespace later (Api::V2::CommentsController) can coexist
  with this file untouched, letting existing API consumers keep using v1
  while v2 is developed.
=end