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

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

templates/pkgbase/merge.html

@@ -49,6 +49,12 @@
                     />
                 </p>
 
+                <p>
+                    <label for="id_comments">{{ "Comments" | tr }}:</label>
+                    <textarea id="id_comments" name="comments"
+                              rows="5" cols="50"></textarea>
+                </p>
+
                 <p>
                     <label class="confirmation">
                         <input type="checkbox" name="confirm" />