Include Tower configurations into activity stream

Relates #7386 of ansible-tower.

Due to the uniqueness of Tower configuration datastore model, it is not
fully compatible with activity stream workflow. This PR introduced
setting field for activitystream model along with other changes to make
Tower configuration a special case for activity streams.

Signed-off-by: Aaron Tan <jangsutsr@gmail.com>

awx/main/models/activity_stream.py

@@ -3,6 +3,7 @@
 
 # Tower
 from awx.api.versioning import reverse
+from awx.main.fields import JSONField
 
 # Django
 from django.db import models
@@ -66,6 +67,8 @@ class ActivityStream(models.Model):
     role = models.ManyToManyField("Role", blank=True)
     instance_group = models.ManyToManyField("InstanceGroup", blank=True)
 
+    setting = JSONField(blank=True)
+
     def get_absolute_url(self, request=None):
         return reverse('api:activity_stream_detail', kwargs={'pk': self.pk}, request=request)