Add food show endpoint

As a user,

I should be able to request the information for a specific food item using a GET request to the endpoint /api/v1/foods/:id, where the ID is a valid food item in the system.

The response should return a 200 status and the food item, matching the following format:
```
{
"id": 1,
"name": "Banana",
"calories": 250
}
```
In the event of a request for a food item that does not exist in the system, the application should return a 404 and a message like the below:
```
{
"message": "Error: Food not found"
}
```

- [x] Tested
- [x] Documented