feat(protocol): define native session credentials

fixtures/invalid/browser-session-native-identity.json

@@ -0,0 +1,10 @@
+{
+  "username": "alice",
+  "provider": "local",
+  "roles": ["user"],
+  "role": "user",
+  "native_identity": {
+    "client_device_id": "device-1",
+    "device_key_id": "key-1"
+  }
+}