Minor fixes to models

src/models/common.py

@@ -8,10 +8,11 @@ PyObjectId = Annotated[str, BeforeValidator(str)]
 
 class BaseMongoModel(BaseModel):
 	"""A base Pydantic model for all MongoDB documents."""
-	id: PyObjectId = Field(..., alias="_id")
+	id: PyObjectId = Field(..., validation_alias="_id")
 
 	model_config = ConfigDict(
 		frozen=True,
 		from_attributes=True,
-		arbitrary_types_allowed=True
+		arbitrary_types_allowed=True,
+		populate_by_name=True
 	)

src/models/session.py

@@ -16,7 +16,11 @@ class Message(BaseModel):
 	timestamp: datetime
 
 	# Use a standard config for this sub-model
-	model_config = ConfigDict(frozen=True, from_attributes=True)
+	model_config = ConfigDict(
+		frozen=True,
+		from_attributes=True,
+		populate_by_name=True
+	)
 
 class Session(BaseMongoModel):
 	"""A Pydantic model for a chat session, including nested messages."""