update db functions according to server routes

[rebeccazhangnz]

Update db functions according to individual route request and response.

Note : Use postman/ console log to check if route and db function has been linked and function properly. Do not write unit test on routes/db, please create new ticket for it if it is needed.

[grantis]

Tested the db functions and server routes with postman and all is working.

// greetings
[
    {
        "id": 5,
        "category_id": "3",
        "english": "Hello",
        "niuean": "Fakaalofa atu"
    },
    {
        "id": 6,
        "category_id": "3",
        "english": "Goodbye",
        "niuean": "Koe kia"
    }
]
// family
[
    {
        "id": 1,
        "category_id": "1",
        "english": "Baby",
        "niuean": "Tama muke"
    },
    {
        "id": 2,
        "category_id": "1",
        "english": "Sibling",
        "niuean": "Lafu"
    }
]
 // food
[
    {
        "id": 3,
        "category_id": "2",
        "english": "Apple",
        "niuean": "Fua apala"
    },
    {
        "id": 4,
        "category_id": "2",
        "english": "Kumara",
        "niuean": "Timala"
    }
]
 // numbers
[
    {
        "id": 7,
        "category_id": "4",
        "english": "Ten",
        "niuean": "Hogofulu"
    },
    {
        "id": 8,
        "category_id": "4",
        "english": "One",
        "niuean": "Taha"
    }
]