create data file containing all drinks' information
create a header file coffee_product.h, which contains class product. In class product, define a variable with data type map<string, pair<long int, double>> which map from name of product to pair of its quantity and its price
When I pass a non-existed information to manager::sign_in(), the functions returns false, which is a proper result. However, CTest failed, while it was meant to return Passed.
Right now, the function manager::new_account() requires inputting while executing that functions. This makes the function either too hard to test or too non-flexible.
To resolve this issue, we should declare a new manager_t variable and pass it as a reference to the function manager::new_account()
Finally, a complete functions will look like this: manager& manager::new_account(manager_t &new_acc)