Use template chunks.
Use and add template chunks to HyperKitty. As per https://gitlab.com/mailman/django-mailman3/merge_requests/8.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Use and add template chunks to HyperKitty. As per https://gitlab.com/mailman/django-mailman3/merge_requests/8.