Explicit path matching and path params for Pages

[sbsoftware]

The previous path matching defaults for Pages was flawed as it always matched a resource-like path both with and without an ID path parameter, like it is for Resources. The issue is that a Page only supports a single view, so it cannot be responsible for an index and a detail view of a resource at the same time. If you want to serve two kinds of pages, you'll have to create two Page sub-classes or use a Resource.
With these changes, the default behavior of a Page is to just match the exact path derived from the path name (LegalNoticePage -> /legal_notice). This can be altered/extended via three macros:

• root_path
  • Sets the matched path at the beginning (root_path "/foo")
• path_param
  • Defines a path parameter with an optional matcher regex (path_param :id, /\d+/) and the end of the currently defined path
  • A method with the given name will be defined that returns the parsed parameter for an instance of the Page
• nested_path
  • Adds a static segment to be matched at the end of the currently defined path

Example:

class PostsPage < ApplicationPage
  root_path "/posts" # redundant as it was already derived from the class name, could be left out
  path_param :id, /\d+/ # the digit-only regex is the default and could be left out
  nested_path "/comments" # leading or trailing slashes could be left out
end

PostsPage will then match paths of this kind: /posts/123/comments, with "123" begin returned by an #id method in the context of the page instance.