"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/forms.py

@@ -121,7 +121,7 @@ class EventForm(forms.ModelForm):
         fields = ['is_rig', 'name', 'venue', 'start_time', 'end_date', 'start_date',
                   'end_time', 'meet_at', 'access_at', 'description', 'notes', 'mic',
                   'person', 'organisation', 'dry_hire', 'checked_in_by', 'status',
-                  'purchase_order', 'collector']
+                  'purchase_order', 'collector', 'forum_url']
 
 
 class BaseClientEventAuthorisationForm(forms.ModelForm):