Port to Drupal 8

with approval of @deekayen, i'm going to take a pass at an upgrade of r4032login to 8.x.

really learned a lot about symfony and d8 from this upgrade!

i'm attaching what i've got so far. this is basically altering the AccessSubscriber service, so r4032login can handle its own 403 exceptions. missing still is...

* exception handling from AccessDeniedHttpException, namely watchdog logs
* rendering of UserLoginForm for match_noredirect_pages config

per suggestions by @damiankloip in IRC, replacing the AccessSubscriber seems overkill. i'll try only listening to the EXCEPTION event in the subscriber instead.

eliminating the altering of AccessSubscriber, this is much simpler.

a few more updates including...

* configuration factory argument in subscriber service
* form validation for r4032login paths
* missing AccessDeniedHttpException dependecy
* Reordered default_redirect_code mappings
* replaced collapsible fieldset with HTML5 details element
* dropped unused page.403 config
* removed uneeded DestructableInterface and destroy method

@deekayen has added me as a maintainer, so i've pushed my work so far up to the 8.x-1.x branch. i'll update the version and make some follow up issues once 8.x gets listed here.

I tested #6 tonight and all the basic functionality from 6.x-1.x worked.

+++ b/lib/Drupal/r4032login/EventSubscriber/R4032LoginSubscriber.php
@@ -0,0 +1,97 @@
+        $response = new RedirectResponse(url($redirect, array('absolute' => TRUE)));

You can inject the urlGenerator here too. Other than that - looking pretty good!

thanks @damiankloip. i've added a task for this in #2210717: Inject the urlGenerator in R4032LoginSubscriber.

I've committed and pushed the new 8.x branch.