Better integration of sqlite3 database

backend/app/crud.py

@@ -0,0 +1,20 @@
+from sqlalchemy.orm import Session, joinedload
+
+def get_shipments(db: Session):
+    from app.models import Shipment
+    return db.query(Shipment).options(
+        joinedload(Shipment.contact_person),
+        joinedload(Shipment.return_address),
+        joinedload(Shipment.proposal),
+        joinedload(Shipment.dewars)
+    ).all()
+
+def get_shipment_by_id(db: Session, shipment_id: str):
+    from app.models import Shipment
+    shipment = db.query(Shipment).options(
+        joinedload(Shipment.contact_person),
+        joinedload(Shipment.return_address),
+        joinedload(Shipment.proposal),
+        joinedload(Shipment.dewars)
+    ).filter(Shipment.shipment_id == shipment_id).first()
+    return shipment