Get the URL to edit a the current page or entry in the Control Panel, if there is one (for example, there is no edit_url for a template route).
The user will need to login and have permissions, so it's probably best if used in conjunction with permissions checks.
<a href="{{ edit_url }}">Edit this page</a><a href="/cp/pages/edit/about-ye-old-me">Edit this page</a>
