Support for Mutation Operation

[shafreenAnfar]

Description:
For more details see here.

[ThisaruGuruge]

Example Implementation of a mutation operation:

import ballerina/graphql;

service /graphql on new graphql:Listener(9000) {
    remote function updateCity(int id, string newCity) returns Person {
        Person p = people[id];
        p.address.city = newCity;
        return p;
    }
}

Person[] people = [
    {
        name: "Walter White",
        age: 51,
        address: {
            number: "308",
            street: "Negra Arroyo Lane",
            city: "Albuquerque"
        }
    }
];

type Person record {|
    string name;
    int age;
    Address address;
|};

type Address record {|
    string number;
    string street;
    string city;
|};

Now, this can be mutated by using the following document:

mutation City {
    updateCity(id: 0, newCity: "New Hampshire") {
        name
        address {
            city
        }
    }
}

The result should be:

{
    "data": {
        "updateCity": {
            "name": "Walter White",
            "address": {
                "city": "New Hampshire"
            }
        }
    }
}

[ThisaruGuruge]

This is currently blocked due to ballerina-platform/ballerina-lang#31581