Add wagtail-purge, cache CDN purge.

hypha/settings/base.py

@@ -132,6 +132,7 @@ INSTALLED_APPS = [
     'rest_framework',
     'rest_framework_api_key',
     'wagtailcache',
+    'wagtail_purge',
     'django_file_form',
 
     'hijack',

requirements.txt

@@ -43,5 +43,6 @@ reportlab==3.5.59
 social_auth_app_django==4.0.0
 tomd==0.1.3
 wagtail-cache==1.0.1
+wagtail-purge==0.1
 wagtail==2.11.5
 whitenoise==5.2.0