Create or update contact

curl --request POST \
  --url https://app.flowella.io/api/v1/contacts \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "phone": "+15551234567",
  "name": "Ada Lovelace",
  "email": "ada@example.com"
}
'

{
  "id": "<string>",
  "phone": "<string>",
  "waId": "<string>",
  "name": "<string>",
  "email": "<string>",
  "isOptedOut": true,
  "createdAt": "<string>",
  "updatedAt": "<string>"
}