better time usings

src/server/models/auth.py

@@ -6,7 +6,7 @@ easy to validate and test.
 """
 from __future__ import annotations
 
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Optional
 
 from pydantic import BaseModel, Field, constr
@@ -53,5 +53,5 @@ class SessionModel(BaseModel):
 
     session_id: str = Field(..., description="Unique session identifier")
     user: Optional[str] = Field(None, description="Username or identifier")
-    created_at: datetime = Field(default_factory=datetime.utcnow)
+    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
     expires_at: Optional[datetime] = Field(None)