feat: user service

gateway/docs/examples.md

@@ -89,6 +89,26 @@ Example `ExecuteCommandResponse`:
 }
 ```
 
+Example authenticated self-service request metadata:
+
+```json
+{
+  "protocolVersion": "v1",
+  "deviceSessionId": "device-session-123",
+  "messageType": "user.account.get",
+  "timestampMs": "1775121600000",
+  "requestId": "request-account-123",
+  "payloadBytes": "RkxBVEJVRkZFUlNfVVNFUl9SRVFVRVNU",
+  "payloadHash": "5fY6Q8V9mK8x2B7v6v0V0m0i1rQ2QF0rQ8V1Yt1r8Ys=",
+  "signature": "3o4v8f3h0Y6I0x1bS7zY+8m0bV1Lk4D3yq8J2n8F1rD7yK9v8M1Q0w2s4a6f8d0Q0m3L6y8R1t5w7x9z0a2cA=="
+}
+```
+
+The external payload remains FlatBuffers. The current `Gateway -> User`
+self-service adapter decodes that payload, calls the trusted internal
+User Service REST API, then re-encodes the returned account aggregate or error
+envelope back into FlatBuffers before signing the response.
+
 Example bootstrap `GatewayEvent` sent after `SubscribeEvents` opens:
 
 ```json