Receive an event when someone joins the campaign

Format Example

{
  "type": "participation",
  "user": {
    "firstname": "Lana",
    "lastname": "Dr.",
    "email": "[email protected]",
    "referralCode": "abc123",
    "createdAt": "2021-04-01 13:00:01"
  },
  "referrer": {
    "firstname": "Nalyssa",
    "lastname": "Gr",
    "email": "[email protected]",
    "referralCode": "dfg456",
    "createdAt": "2021-04-01 13:00:00"
  }
}