"Create forum post" button on a rig page (#551)

* Add button for creating forum thread draft from event detail

TODO: Allow RIGS to ingest POST requests sent from the forum on new posts in RIG info to link up the forum thread

RE https://forum.nottinghamtec.co.uk/t/rigs-discourse-integration/15592/21

* Mockup webhook recieving view

* Correct method of CRSF exemption for webhook reciever

* Use f-strings correctly, not like a big dumb

* That was also dumb, fix that too

* Second shot at webhook reciever

* Oops

* >.<

* Third shot

* Try again at signing

* What if I gave it the right arguments. That might be a good start.

* More fiddling with auth

* Add debug print

* Okay, put that back where it was because I inavertently overloaded my import

Flashbacks to my java days...

* Different header access method

* Fix import, again

* Fix ommited json parsing wotsit

* Fix url

* Fix string index

* Correct template logic

* Allow manual adding/editing of URLs

* Filter by right flavour of event

* Amend event str conversion for consistency

* Oops

* Make migration

Will be squashed later

* Fix logic when creating events

* Squash migration

* Implement codedoctor suggestion

RIGS/urls.py

@@ -110,6 +110,9 @@ urlpatterns = [
     path('event/<int:pk>/checkin/add/', login_required(views.EventCheckInOverride.as_view()),
          name='event_checkin_override'),
 
+    path('event/<int:pk>/thread/', permission_required_with_403('RIGS.change_event')(views.CreateForumThread.as_view()), name='event_thread'),
+    path('event/webhook/', views.RecieveForumWebhook.as_view(), name='webhook_recieve'),
+
     # Finance
     path('invoice/', permission_required_with_403('RIGS.view_invoice')(views.InvoiceIndex.as_view()),
          name='invoice_list'),