feat(base_handler.py): add BaseHandler class for message handling

src/judas_server/backend/handler/base_handler.py

@@ -0,0 +1,41 @@
+# -*- coding: utf-8 -*-
+from __future__ import annotations
+
+import logging as lg
+from typing import TYPE_CHECKING
+
+from judas_server.backend.client import Client
+
+if TYPE_CHECKING:
+    from judas_protocol import Message
+
+    from judas_server.backend import BackendServer
+
+
+class BaseHandler:
+    """BaseHandler is the base class for all message handlers in the backend server.
+
+    It defines the interface for handling messages and provides common functionality for all handlers.
+    """
+
+    def __init__(self, backend_server: BackendServer) -> None:
+        """Initialize the BaseHandler with a reference to the backend server.
+
+        Args:
+            backend_server (BackendServer): The backend server instance that this handler belongs to.
+        """
+        self.logger: lg.Logger = lg.getLogger(
+            f"{__name__}.{self.__class__.__name__}"
+        )
+        self.backend_server: BackendServer = backend_server
+
+    def handle(self, client: Client, message: Message) -> None:
+        """Handle a message from a client.
+
+        This method must be implemented by subclasses to define the specific handling logic for different message types.
+
+        Args:
+            client (Client): The client that sent the message.
+            message (Message): The message to be handled.
+        """
+        raise NotImplementedError("handle() must be implemented by subclasses")