"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/templates/partials/event_details.html

@@ -77,6 +77,15 @@
                 <dt class="col-sm-6">PO</dt>
                 <dd class="col-sm-6">{{ object.purchase_order }}</dd>
             {% endif %}
+
+            <dt class="col-6">Forum Thread</dt>
+            {% if object.forum_url %}
+            <dd class="col-6"><a href="{{object.forum_url}}">{{object.forum_url}}</a></dd>
+            {% else %}
+            <a href="{% url 'event_thread' object.pk %}" class="btn btn-primary" title="Create Forum Thread"><span
+            class="fas fa-plus"></span> <span
+            class="hidden-xs">Create Forum Thread</span></a>
+            {% endif %}
         </dl>
     </div>
 </div>