curl --request PUT \
  --url https://api.heyy.io/api/v2.0/contacts/{contactId} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "firstName": "<string>",
  "lastName": "<string>",
  "labels": [
    {
      "name": "<string>"
    }
  ],
  "attributes": [
    {
      "externalId": "<string>",
      "value": "<string>"
    }
  ]
}
'

{
  "data": {
    "id": "<string>",
    "createdAt": "<string>",
    "updatedAt": "<string>",
    "firstName": "<string>",
    "lastName": "<string>",
    "phoneNumber": "<string>",
    "email": "<string>",
    "labels": [
      "<string>"
    ],
    "attributes": [
      {
        "name": "<string>",
        "value": "<string>"
      }
    ]
  }
}