Resume an SMS campaign

curl -X POST 'https://www.unitpost.com/api/v1/sms/campaigns/cmp_123/resume' \
  -H 'Authorization: Bearer YOUR_API_KEY' \
  -H 'User-Agent: my-app/1.0'

{
  "object": "sms_campaign",
  "id": "id_123",
  "name": "Example",
  "status": "draft",
  "type": "marketing",
  "template_id": "template_123",
  "segment_id": "segment_123",
  "sender_id": "sender_123",
  "topic_id": "topic_123",
  "routing": "automatic",
  "scheduled_at": "2026-01-01T00:00:00.000Z",
  "hold": {
    "reason": "scheduled",
    "until": "string"
  },
  "projected_recipients": {
    "total": 1,
    "reachable": 0,
    "skipped": 0
  },
  "recipient_count": 1,
  "variable_fallbacks": {},
  "excluded_contact_ids": [
    "string"
  ],
  "started_at": "2026-01-01T00:00:00.000Z",
  "completed_at": "2026-01-01T00:00:00.000Z",
  "canceled_at": "2026-01-01T00:00:00.000Z",
  "created_at": "2026-01-01T00:00:00.000Z",
  "updated_at": "2026-01-01T00:00:00.000Z"
}