Added docs and test

Packages/com.darkmattergameproduction.com.darkmatter.fonepay-unity/Editor/FonepaySecretsStore.cs

@@ -0,0 +1,42 @@
+using UnityEditor;
+using UnityEngine;
+
+namespace Darkmatter.Fonepay.Editor
+{
+    /// <summary>
+    /// Per-project secret storage backed by EditorPrefs.
+    /// Keys are namespaced with project path hash so different machines/projects never collide.
+    /// EditorPrefs lives in OS user store (Keychain on macOS, registry on Windows) — not in repo.
+    /// </summary>
+    public static class FonepaySecretsStore
+    {
+        private const string PrefixBase = "Darkmatter.Fonepay.";
+
+        private static string ProjectKey =>
+            PrefixBase + Application.dataPath.GetHashCode().ToString("X") + ".";
+
+        public static string PasswordKey  => ProjectKey + "Password";
+        public static string SecretKeyKey => ProjectKey + "SecretKey";
+
+        public static string GetPassword()  => EditorPrefs.GetString(PasswordKey,  string.Empty);
+        public static string GetSecretKey() => EditorPrefs.GetString(SecretKeyKey, string.Empty);
+
+        public static void SetPassword(string v)  => EditorPrefs.SetString(PasswordKey,  v ?? string.Empty);
+        public static void SetSecretKey(string v) => EditorPrefs.SetString(SecretKeyKey, v ?? string.Empty);
+
+        public static void Clear()
+        {
+            EditorPrefs.DeleteKey(PasswordKey);
+            EditorPrefs.DeleteKey(SecretKeyKey);
+        }
+
+        public static bool HasAll() =>
+            !string.IsNullOrEmpty(GetPassword()) && !string.IsNullOrEmpty(GetSecretKey());
+
+        [InitializeOnLoadMethod]
+        private static void RegisterRuntimeProvider()
+        {
+            FonepayConfig.EditorSecretsProvider = () => (GetPassword(), GetSecretKey());
+        }
+    }
+}