Or for a coffee order maybe consider that the order and the payment could be independent resources, thus you get

gistfile1.json

{
  "_links": {
    "self": {
      "href": "/api/orders/123"
    },
    "profile": {
       "href": "/profiles/order"
     }
    "/rels/payments": {
      "href": "/api/orders/123/payments",
      "profile": "/profiles/order/payments"
    }
  }
}

gistfile2.json

{
  "_links": {
    "self": {
      "href": "/api/orders/123/payments"
    },
    "profile": {
      "href": "/profiles/order/payments"
    },
    "/rels/create-form": {
      "href": "/forms/order/payment/create",
      "profile": "/profiles/form"
    },
    "/rels/create": {
      "href": "/api/orders/123/payments",
      "profile": "/profiles/order/payment/create"
    }
  },
  "_embedded": {
    "payment": [
      {
        "_links": {
          "self": {
            "href": "/api/orders/123/payments/1001"
          },
          "profile": {
            "href": "/profiles/order/payment"
          }
        },
        "type": "credit-card",
        "amount": "5.50",
        "currency": "NZD",
        "status": "declined",
        "reason": "invalid card details"
      }
    ]
  }
}