Add contacts to a campaign

curl --request POST \
  --url https://api.vocobase.com/api/v2/campaigns/{id}/contacts \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "contacts": [
    {
      "phone": "+919876543210",
      "name": "Asha Kumar",
      "metadata": {
        "tier": "gold"
      }
    },
    {
      "phone": "+14155551234",
      "name": "Jordan Lee"
    }
  ]
}
'

{
  "success": true,
  "data": {
    "added": 1498,
    "duplicates": 2,
    "contacts_created": 1300,
    "contacts_existing": 198
  }
}