dmails: allow marking dmails as unread.

* Add ability to mark dmails as unread.
* Fix users.unread_dmail_count to not count deleted dmails.
* Fix show action so that API calls don't mark dmails as read.
* Don't show the unread dmail notice on the /dmails page itself.
* Stop using users.has_mail flag.

app/controllers/dmails_controller.rb

@@ -22,7 +22,7 @@ class DmailsController < ApplicationController
   def show
     @dmail = Dmail.find(params[:id])
     check_privilege(@dmail)
-    @dmail.mark_as_read!
+    @dmail.update!(is_read: true) if request.format.html?
     respond_with(@dmail)
   end
 
@@ -41,10 +41,8 @@ class DmailsController < ApplicationController
   end
 
   def mark_all_as_read
-    Dmail.visible.unread.each do |x|
-      x.update_column(:is_read, true)
-    end
-    CurrentUser.user.update(has_mail: false, unread_dmail_count: 0)
+    @dmails = CurrentUser.user.dmails.mark_all_as_read
+    respond_with(@dmails)
   end
 
   private