Add sample for app testing

Assets/.gitkeep

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+# Keeps Assets folder in git so Unity recognizes the project as valid.

Assets/Resources/BillingMode.json

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+{"androidStore":"GooglePlay"}

Assets/StashLinkGenerator.cs

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+using System;
+using UnityEngine;
+using UnityEngine.Networking;
+using System.Collections;
+using System.Text;
+
+/// <summary>
+/// Fetches URLs from the Stash API using the provided API key (set in the Inspector).
+/// Intended for sample usage only. For production, always generate Stash URLs securely on your backend.
+/// </summary>
+public class StashLinkGenerator : MonoBehaviour
+{
+    #region API Calls
+
+    private const string QUICK_PAY_ENDPOINT = "https://test-api.stash.gg/sdk/server/checkout_links/generate_quick_pay_url";
+    private const string AUTHENTICATED_URL_ENDPOINT = "https://test-api.stash.gg/sdk/server/generate_url";
+
+    [SerializeField] private string apiKey = "YOUR_STASH_API_KEY";
+
+    /// <summary>Request a quick pay checkout URL. See https://docs.stash.gg/api/server-quickpay/GenerateQuickPayUrl for reference.</summary>
+    public void RequestCheckoutUrl(Action<string> onUrl, Action<string> onError)
+    {
+        StartCoroutine(RequestCheckoutUrlCoroutine(onUrl, onError));
+    }
+
+    private IEnumerator RequestCheckoutUrlCoroutine(Action<string> onUrl, Action<string> onError)
+    {
+        // Determine purchase platform dynamically
+        string platformValue;
+#if UNITY_IOS
+            platformValue = "IOS";
+#elif UNITY_ANDROID
+            platformValue = "ANDROID";
+#else
+        platformValue = Application.platform.ToString().ToUpper();
+#endif
+
+        var request = new QuickPayRequest
+        {
+            regionCode = "USA",
+            currency = "USD",
+            item = new QuickPayItem
+            {
+                id = "test_item_id",
+                pricePerItem = "0.99",
+                quantity = 1,
+                imageUrl = "https://storage.googleapis.com/stash_assets/stash_logo_128.png",
+                name = "Test Item",
+                description = "A description of the test item"
+            },
+            user = new QuickPayUser
+            {
+                id = "test_user_id",
+                validatedEmail = "test@domain.com",
+                platform = platformValue
+            }
+        };
+
+        byte[] body = Encoding.UTF8.GetBytes(JsonUtility.ToJson(request));
+        using (var www = new UnityWebRequest(QUICK_PAY_ENDPOINT, "POST"))
+        {
+            www.uploadHandler = new UploadHandlerRaw(body);
+            www.downloadHandler = new DownloadHandlerBuffer();
+            www.SetRequestHeader("Content-Type", "application/json");
+            www.SetRequestHeader("X-Stash-Api-Key", apiKey);
+            yield return www.SendWebRequest();
+
+            if (www.result == UnityWebRequest.Result.Success)
+            {
+                var response = JsonUtility.FromJson<QuickPayResponse>(www.downloadHandler.text);
+                onUrl?.Invoke(response.url);
+            }
+            else
+            {
+                onError?.Invoke(www.error);
+            }
+        }
+    }
+
+    /// <summary>Request a pre-authenticated webshop URL. See https://docs.stash.gg/api/server-urls/GenerateAuthenticatedUrl for reference.</summary>
+    /// <param name="target">Target destination: "DEFAULT", "HOME", "LOYALTY", "ROOT", or "STORE"</param>
+    public void RequestAuthenticatedWebshopUrl(Action<string> onUrl, Action<string> onError, string target = "HOME")
+    {
+        StartCoroutine(RequestAuthenticatedWebshopUrlCoroutine(onUrl, onError, target));
+    }
+
+    private IEnumerator RequestAuthenticatedWebshopUrlCoroutine(Action<string> onUrl, Action<string> onError, string target)
+    {
+        var request = new AuthenticatedUrlRequest
+        {
+            user = new AuthenticatedUrlUser { id = "WEBSHOP_USER_ID" },
+            target = target
+        };
+
+        byte[] body = Encoding.UTF8.GetBytes(JsonUtility.ToJson(request));
+        using (var www = new UnityWebRequest(AUTHENTICATED_URL_ENDPOINT, "POST"))
+        {
+            www.uploadHandler = new UploadHandlerRaw(body);
+            www.downloadHandler = new DownloadHandlerBuffer();
+            www.SetRequestHeader("Content-Type", "application/json");
+            www.SetRequestHeader("X-Stash-Api-Key", apiKey);
+            yield return www.SendWebRequest();
+
+            if (www.result == UnityWebRequest.Result.Success)
+            {
+                var response = JsonUtility.FromJson<AuthenticatedUrlResponse>(www.downloadHandler.text);
+                onUrl?.Invoke(response.url);
+            }
+            else
+            {
+                onError?.Invoke(www.error);
+            }
+        }
+    }
+
+    #endregion
+
+    #region API models
+
+    [Serializable] private class QuickPayRequest { public string regionCode; public string currency; public QuickPayItem item; public QuickPayUser user; }
+    [Serializable] private class QuickPayItem { public string id; public string pricePerItem; public int quantity; public string imageUrl; public string name; public string description; }
+    [Serializable] private class QuickPayUser { public string id; public string validatedEmail; public string regionCode; public string platform; }
+    [Serializable] private class QuickPayResponse { public string id; public string url; public string regionCode; }
+    [Serializable] private class AuthenticatedUrlRequest { public AuthenticatedUrlUser user; public string target; }
+    [Serializable] private class AuthenticatedUrlUser { public string id; }
+    [Serializable] private class AuthenticatedUrlResponse { public string url; }
+
+    #endregion
+}