Create a decorator or
require_access alternative that allows the page to render but causes a login overlay dialog to be displayed over the page, similar to this mockup.
The overlay should load an iframe from the URL specified in
auth.login_fragment_url with the appropriate
return_to info provided, which should submit to
_top to reload the source page.
Also, the overlay should be a little lighter than the mockup and the box should be movable so that the underlying page can be inspected (although not interacted with) as the purpose behind this is to showcase what can be done when logged in.
A default fragment implementation should be provided based on the default login view in
allura.controllers.auth.AuthController. A SFX fragment implementation will need to be created, as well, for SF.