One to Many relationship real life example - django

Question

I am trying to design the schema. I am confused about should I use one-to-many or many-to-one relationships.
My use case is somewhat like customers ordering the food.
There are 2 customers and 5 food items
Customers: [John, Alice]
Food: [Rice, Noodle, Chicken, Beacon, Ice-cream]
Use case: One Customer can order many items, but if first customer orders that item, it can not be ordered by other.
Example:
John orders -> Rice, Noodle, Chicken
Alice orders -> Beacon, Ice-cream
**This is valid, both customers ordered unique food.**
Example:
John orders -> Rice, Noodle, Chicken
Alice orders -> Beacon, Ice-cream, Chicken
**This is invalid, because Chicken is being ordered twice. John Already ordered chicken so Alice can not order it.**
Note: I am trying to this in mongodb documents and trying to establish relationship using Django models.

Answer 1

One way to handle this would be to create a junction table CustomerFood which looks something like this:
CREATE TABLE CustomerFood (
Customer varchar(255) NOT NULL,
Food varchar(255) NOT NULL,
PRIMARY KEY(Customer, Food)
);
The above table definition alone would only ensure that each customer can be related to each food at most once. To enforce the additional restriction that a given food can be associated with only one customer, we can add a unique constraint on the Food column:
ALTER TABLE CustomerFood ADD CONSTRAINT food_unique UNIQUE (Food);

Answer 2

Using Django templates:
You could use many to many in django (less code bit more complex to understand) OR create "table in the
middle approch" (more manual approach that needs more model code).
Django many to many documentation
Secondly you should use Validators to
ensure your logic that one person can only order one dish, and the
dishes will sell out, this is more programming logic and can be part
of a validator. Django validators documentation