Add refund support via entitlement IDs

[Copilot]

Implements the /game/refund/v1 refund endpoint, allowing players to refund previously purchased items by their entitlement IDs.

New types (PurchaseRequest.cs)

• LootLockerRefundByEntitlementIdsRequest – request payload
• LootLockerRefundByEntitlementIdsResponse – full response with inventory events, currency credited/clawed back, and per-entitlement warnings
• Supporting models: LootLockerRefundInventoryEvent, LootLockerRefundCurrencyEntry, LootLockerRefundWarning, LootLockerRefundWarningDetail, LootLockerRefundNonReversibleReward

New endpoint (LootLockerEndPoints.cs)

public static EndPointClass refundByEntitlementIds = new EndPointClass("game/refund/v1", LootLockerHTTPMethod.POST);

New SDK method (LootLockerSDKManager.cs)

LootLockerSDKManager.RefundByEntitlementIds(
    new[] { "entitlementUlid1", "entitlementUlid2" },
    response => {
        // response.player_inventory_events – assets removed or skipped
        // response.currency_refunded      – purchase price returned
        // response.currency_clawback      – currency rewards reclaimed
        // response.warnings               – non-fatal issues per entitlement
    }
);

A non-empty warnings array does not indicate failure — it signals partial reversal (e.g. non-reversible progression rewards, insufficient funds for clawback). The method validates that entitlementIds is non-null and non-empty before making the API call.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add support for refunds</issue_title>
<issue_description>### Purpose

Reflect the backend implementation of the refunds feature
Acceptance Criteria

• All refund endpoints have implementations in the relevant SDKs
• Public SDK api surface is well documented in code documentation
• Functionality is tested and working end to end

APIDog collaboration link

https://app.apidog.com/link/project/446496/apis/api-28123628

Public API docs link

https://ref.lootlocker.com/game/refund-items-by-entitlement-ids-api-28123628

An in issue OpenAPI spec of the relevant API surface

{   "openapi": "3.1.0",   "info": {     "title": "Default module",     "description": "Async virtual-currency purchasing endpoints for game clients. Purchases are initiated with a 202 response and polled for completion via the status endpoint. Failed purchases can be retried.\n",     "version": "1.0.0"   },   "tags": [],   "paths": {     "/game/refund/v1": {       "post": {         "summary": "Refund items by Entitlement IDs",         "deprecated": false,         "description": "",         "tags": [],         "parameters": [           {             "name": "Content-Type",             "in": "header",             "description": "",             "required": true,             "example": "application/json",             "schema": {               "type": "string"             }           }         ],         "requestBody": {           "content": {             "application/json": {               "schema": {                 "type": "object",                 "properties": {                   "entitlement_ids": {                     "type": "array",                     "items": {                       "$ref": "#/components/schemas/ULID"                     }                   }                 },                 "required": [                   "entitlement_ids"                 ]               },               "examples": {}             }           },           "required": true         },         "responses": {           "200": {             "description": "",             "content": {               "application/json": {                 "schema": {                   "type": "object",                   "properties": {                     "player_inventory_events": {                       "type": "array",                       "description": "Assets that were added or removed from the player's inventory as part of the refund",                       "items": {                         "type": "object",                         "properties": {                           "asset_id": {                             "type": "integer",                             "description": "The legacy numeric ID of the asset",                             "format": "uint64"                           },                           "name": {                             "type": "string",                             "description": "Display name of the asset"                           },                           "action": {                             "type": "string",                             "enum": [                               "removed",                               "skipped"                             ],                             "description": "`removed` if the asset was successfully taken back from the player's inventory. `skipped` if it could not be removed (e.g. already consumed or transferred)."                           }                         },                         "required": [                           "asset_id",                           "name",                           "action"                         ]                       }                     },                     "currency_refunded": {                       "type": "array",                       "description": "Currency amounts credited back to the player's wallet (i.e. the purchase price being returned)",                       "items": {                         "$ref": "#/components/schemas/Currency%20Entry"                       }                     },                     "currency_clawback": {                       "type": "array",                       "description": "Currency amounts debited from the player's wallet (i.e. currency rewards from the entitlement being reclaimed)",                       "items": {                         "$ref": "#/components/schemas/Currency%20Entry"                       }                     },                     "warnings": {                       "type": "array",                       "description": "Warnings encountered during refund processing, grouped by entitlement. A non-empty warnings array does not mean the refund failed — it means some aspects could not be fully reversed.",                       "items": {                         "type": "object",                         "properties": {                           "entitlement_id": {      ...

</details>



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- Fixes lootlocker/index#1395

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