Add denial reason when redirecting manually accessed pages to login action

When users manually accessed a URL that they do not have view permission for, they are redirected to the Login action, but no explanation is provided. Redirecting to unexpected pages should provide a reason.

When the login action receives an os_destination, it should provide an error message indicating "You must login to access this page"

Optionally, the Login action can parse the context path to check if the URL is a Confluence page and list the page title attempting to be accessed. For example, on
http://localhost:8080/login.action?os_destination=%2Fdisplay%2Fds%2FHome

You must login to access 'Home'