I'm purchasing some item using the following code (example from BrainCloud API reference):

_bc.UserItemsService.PurchaseUserItem(defId, quantity, shopId, includeDef, successCallback, failureCallback);

I get the following JSON in response (example from BrainCloud API reference):

{
  "data": {
    "items": {
      "8e12e907-3f54-4971-b84a-b685ce50b684": {
        "itemId": "8e12e907-3f54-4971-b84a-b685ce50b684",
        "defId": "boost_rapidfire",
        "quantity": 1,
        "usesLeft": null,
        "coolDownStart": -1,
        "recoveryStart": -1,
        "itemData": {},
        "giftedTo": null,
        "giftedFrom": null,
        "blockId": null,
        "createdAt": 1566850132554,
        "updatedAt": 1566850132554,
        "version": 1,
        "maxUses": null,
        "coolDownUntil": -1,
        "recoveryUntil": -1,
        "itemDef": {
          "defId": "boost_rapidfire",
          "name": "Rapid Fire",
          "desc": "Rapid fire for the next match.",
          "type": "ITEM",
          "category": "boost",
          "tags": null,
          "buyPrice": {
            "coins": 200
          },
          "sellPrice": {},
          "image": null,
          "resourceGroup": null,
          "resourceTag": null,
          "meta": {},
          "pState": "PUBLISHED",
          "publishedAt": 1566850042148,
          "stackable": false,
          "consumable": false,
          "uses": null,
          "coolDownSecs": 0,
          "recoverySecs": 0,
          "activatable": true,
          "statusName": "boosted",
          "activeSecs": 900000,
          "tradable": false,
          "blockchain": false,
          "blockchainDefId": null
        }
      }
    },
    "currencySpent": {
      "coins": 200
    },
    "currencyBalances": {
      "createdAt": 1566850026783,
      "currencyMap": {
        "coins": {
          "consumed": 200,
          "balance": 2999800,
          "purchased": 0,
          "awarded": 3000000
        }
      },
      "playerId": "55ffc16e-f92b-44f3-98b0-68a7a4f24106",
      "updatedAt": 1566850132552
    }
  },
  "status": 200
}

Basically we have the following hierarchy of JSON keys: data.items["8e12e907-3f54-4971-b84a-b685ce50b684"].itemId and so on.
The problem with this response is it uses UUID 8e12e907-3f54-4971-b84a-b685ce50b684 as a JSON key which is obviously not known in advance. Hence, I cannot use built-in Unity's JsonUtility library to map this JSON response to a C# object, like this:

[System.Serializable]
private class PurchaseUserItemSuccessResponse {
    public Data data;
    [System.Serializable]
    public class Data {
        public Items items;
        [System.Serializable]
        public class Items {
            // The problem:
            // Can't define specific items here
            // because their keys are not known in advance
        }
    }
}

Of course, I can try to use some preprocessing tricks or to utilize external JSON library to overcome the issue, but still, using dynamic keys in JSON response for me looks like a bad practice because it creates unnecessary obstacles. It would be simpler to expect solid JSON keys structure. As a developer, for this specific case, I would have liked to see results as a simple array, like this:

{
  "data": {
    "items": [
        "itemId": "8e12e907-3f54-4971-b84a-b685ce50b684",
        "defId": "boost_rapidfire",
        "quantity": 1,
        "usesLeft": null,
        "coolDownStart": -1,
        "recoveryStart": -1,
        "itemData": {},
        "giftedTo": null,
        "giftedFrom": null,
        "blockId": null,
        "createdAt": 1566850132554,
        "updatedAt": 1566850132554,
        "version": 1,
        "maxUses": null,
        "coolDownUntil": -1,
        "recoveryUntil": -1,
        "itemDef": {
          "defId": "boost_rapidfire",
          "name": "Rapid Fire",
          "desc": "Rapid fire for the next match.",
          "type": "ITEM",
          "category": "boost",
          "tags": null,
          "buyPrice": {
            "coins": 200
          },
          "sellPrice": {},
          "image": null,
          "resourceGroup": null,
          "resourceTag": null,
          "meta": {},
          "pState": "PUBLISHED",
          "publishedAt": 1566850042148,
          "stackable": false,
          "consumable": false,
          "uses": null,
          "coolDownSecs": 0,
          "recoverySecs": 0,
          "activatable": true,
          "statusName": "boosted",
          "activeSecs": 900000,
          "tradable": false,
          "blockchain": false,
          "blockchainDefId": null
      ]
    },
    "currencySpent": {
      "coins": 200
    },
    "currencyBalances": {
      "createdAt": 1566850026783,
      "currencyMap": {
        "coins": {
          "consumed": 200,
          "balance": 2999800,
          "purchased": 0,
          "awarded": 3000000
        }
      },
      "playerId": "55ffc16e-f92b-44f3-98b0-68a7a4f24106",
      "updatedAt": 1566850132552
    }
  },
  "status": 200
}

Mapping this response to a C# object is trivial.