-get only contract ID from frontned
-calculate the final price on the backend
-in a transaction, only .save code. No other code due to lock of entities
-delivered date: null to be outside of find as a separate check. If the contract is already closed, it should throw a descriptive error
-get only contract ID from frontned -calculate the final price on the backend -in a transaction, only .save code. No other code due to lock of entities -delivered date: null to be outside of find as a separate check. If the contract is already closed, it should throw a descriptive error