Retrieve a customer

curl --request GET \
  --url https://api.amberflow.io/v1/customers/{customer_id} \
  --header 'X-API-Key: <api-key>'

{
  "id": "cus_sT1gLxE0pV0kafKv",
  "created_at": "2024-09-23T12:00:00.000Z",
  "name": "John Doe",
  "email": "john@example.com",
  "language": "en-US",
  "group_id": "grp_hfc0LgNhTBuWS1j0"
}