feat(api): add Notification schema and document notification streams

gns3server/api/responses.py

@@ -0,0 +1,41 @@
+#
+# Copyright (C) 2026 GNS3 Technologies Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from typing import Any
+
+from fastapi.responses import JSONResponse
+
+from gns3server import schemas
+
+NDJSON_MEDIA_TYPE = "application/x-ndjson"
+
+
+class NDJSONResponse(JSONResponse):
+    """
+    Only used as the response_class of streaming routes to publish the application/x-ndjson media type
+    and the schema of the streamed objects in the OpenAPI document.
+    """
+
+    media_type = NDJSON_MEDIA_TYPE
+
+
+NOTIFICATION_STREAM_RESPONSES: dict[int | str, dict[str, Any]] = {
+    200: {
+        "model": schemas.Notification,
+        "description": "Stream of notifications, one JSON object per line. "
+        "Each line is a Notification, the first one is a ping and then a ping is sent at least every 5 seconds.",
+    }
+}