UpdateCampaignRequest

Resolve the acting org (instance on update, request otherwise) and stamp it on attrs.

Shared by the create/update serializers so the org-resolution boilerplate lives in one place.

{ "name": "string", "message_data": { "whatsapp_id": "string", "template": { "name": "string" }, "template_header_url": "string", "property1": "string", "property2": "string" }, "campaign_list": "string", "campaign_status": "string", "channel_type": "WHATSAPP", "scheduled_at": "2019-08-24T14:15:22.123Z", "category": "PROMOTIONS" }