refactor: Use MongoDB singleton for connection management

application/core/mongo_db.py

@@ -0,0 +1,25 @@
+from application.core import settings
+from pymongo import MongoClient
+from flask import current_app, g
+
+
+class MongoDB:
+    _client = None
+
+    @classmethod
+    def get_client(cls):
+        """
+        Get the MongoDB client instance, creating it if necessary.
+        """
+        if cls._client is None:
+            cls._client = MongoClient(settings.MONGO_URI)
+        return cls._client
+
+    @classmethod
+    def close_client(cls):
+        """
+        Close the MongoDB client connection.
+        """
+        if cls._client is not None:
+            cls._client.close()
+            cls._client = None