Added docs and test

Packages/com.darkmattergameproduction.com.darkmatter.fonepay-unity/Documentation/Fonepay Unity.md

@@ -0,0 +1,36 @@
+# Fonepay Unity
+
+See [README](../README.md) for setup, API reference, and examples.
+
+## Architecture
+
+| Layer | Type | Purpose |
+|---|---|---|
+| Public | `FonepayClient` | Façade. Auto-loads config + secrets. |
+| API | `FonepayApiClient` | Signed REST calls (QR, status, tax refund). |
+| Websocket | `FonepayWebsocketClient` | Receive-loop for QR verification + payment frames. |
+| Crypto | `HmacSha512Signer` | HMAC-SHA512 dataValidation. |
+| Models | `QrRequest`/`QrResult`/`QRPaymentStatus`/... | Serializable DTOs. |
+
+## Flow
+
+```
+PurchaseAsync(req)        ── POST QR ──▶  QrResult { qrCode, thirdpartyQrWebSocketUrl }
+AwaitPaymentAsync(url)    ── WS    ──▶  QRPaymentStatus { Outcome }
+                                           ├─ qrVerified frame → onQrVerified callback
+                                           └─ paymentSuccess frame → resolve
+```
+
+## Outcome rules
+
+| `success` | `paymentSuccess` | `Outcome` |
+|---|---|---|
+| true  | true  | Complete |
+| true  | false | CancelledByUser |
+| false | *     | Failed |
+
+## Termination
+
+- Payment frame received → resolve normally.
+- `CancellationToken` cancelled → `OperationCanceledException`, socket disconnects.
+- Server closes socket before payment → `InvalidOperationException`.