Fix PackageRequest-based notifications

fix(requests): rework handling of requests

This commit changes several things about how we were handling package requests.

Modifications (requests):

• /requests/{id}/close no longer provides an Accepted selection. All manual request closures will cause a rejection.
• Relevent pkgbase actions now trigger request closures: /pkgbase/{name}/delete (deletion), /pkgbase/{name}/merge (merge) and /pkgbase/{name}/disown (orphan).
• Comment fields have been added to /pkgbase/{name}/{delete,merge,disown}, which is used to set the PackageRequest.ClosureComment on pending requests. If the comment field is left blank, a closure comment is autogenerated.
• Autogenerated request notifications are only sent out once as a closure notification.
• Some markup has been fixed.

Modifications (disown/orphan):

• Orphan requests are now handled through the same path as deletion/merge.
• We now check for due date when disowning as non-maintainer; previously, this was only done for display and not functionally. This check applies to Trusted Users' disowning of a package.

This style of notification flow does reduce our visibility, but accounting can still be done via the close request; it includes the action, pkgbase name and the user who accepted it.

Closes #204 (closed)

Signed-off-by: Kevin Morris kevr@0cost.org