Introduce default auto field setting (django 4.1 compatibility)

This removes a compatibility warning (Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField') for django 4.1

AKPlanning/settings.py

@@ -99,6 +99,8 @@ TEMPLATES = [
 
 WSGI_APPLICATION = 'AKPlanning.wsgi.application'
 
+DEFAULT_AUTO_FIELD = 'django.db.models.AutoField'
+
 # Database
 # https://docs.djangoproject.com/en/2.2/ref/settings/#databases