Add Memory Gateway agent plugin

plugins/memory-gateway-agent/memory_gateway_plugin/schemas.py

@@ -0,0 +1,14 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Any
+
+
+@dataclass
+class AgentContext:
+    user_id: str
+    agent_id: str = ""
+    workspace_id: str = ""
+    session_id: str = ""
+    metadata: dict[str, Any] = field(default_factory=dict)
+