Make shipment fields optional and refactor test scripts.

Updated the `number_of_pucks` and `number_of_samples` fields in the `schemas.py` to be optional for greater flexibility. Simplified the test Jupyter Notebook by restructuring imports and consolidating function calls for better readability and maintainability.

backend/app/schemas.py

@@ -493,8 +493,8 @@ class DewarBase(BaseModel):
     dewar_serial_number_id: Optional[int] = None
     unique_id: Optional[str] = None
     tracking_number: str
-    number_of_pucks: int
-    number_of_samples: int
+    number_of_pucks: Optional[int] = None
+    number_of_samples: Optional[int] = None
     status: str
     ready_date: Optional[date]
     shipping_date: Optional[date]