typescripted builder for mocks, making the differentations easy while working

builder typed for mocks

```
// thanks to Olga
const merge = require('deepmerge');
type DeepPartial<T> = T extends object
    ? { [K in keyof T]?: DeepPartial<T[K]> }
    : T;
export type TBuilder<O> = (attrs?: DeepPartial<O>) => O;
const overwriteMerge = <T extends any>(
    destinationArray: T[],
    sourceArray: T[],
): T[] => sourceArray;

export const builderFor = <O extends {}>(defaults: O): TBuilder<O> => attrs =>
    merge(defaults, attrs || {}, { arrayMerge: overwriteMerge });
```

Now mocking becomes easy, you create a base and add differentations on them. They are all typed

```
export const ProductBuilder = builderFor<Product>({
    id: 350395,
    control: {
        theme: ProductTheme.FOO,
        type: ProductControlType.DEFAULT,
    },
    title: 'Mexicaanse kip met salsa',
    link:
        '/mexicaanse-kip-met-salsa',
    availabilityLabel: { text: 'Niet meer bestelbaar' },
    orderable: false,
    propertyIcons: [],
    images: [
        {
            height: 200,
            width: 200,
            url:
                '000089582_001_350395_200.jpg?options=399,q85'
        },
        {
            height: 708,
            width: 708,
            url:
                '000089580_001_350395_708.jpg?options=399,q85'
        },
    ],
    price: { now: 9.95, unitSize: '2 personen' },
    theme: ProductTheme.BAR,
    selectLabel: '2 personen',
    hqId: 643434345,
    gtins: [0, 4534534553],
    brand: 'Foo',
    summary: 'summary',
    availableOnline: true,
});

const PRODUCT_NOT_AVAILABLE_ONLINE = ProductBuilder({
    id: 48340,
    availableOnline: false,
});
```