Provide an identity function to make filtering lists of objects easier

[jan-molak]

Serenity/JS should provide a Screenplay Pattern-style identity function to make it easier to filter lists of objects, e.g. in API tests.

For example:

interface Person {
  name: string;
}

const entries = [ { name: 'Alice' }, { name: 'Bob' }, { name: 'Clarice' } ];

const list = List.of(items);

await actorCalled('Lisa').attemptsTo(
  Ensure.that(
    List.of<Person>(entries)
      .where(List.entry<Person>().name, endsWith('ice')),
    equals([
      'Alice',
      'Clarice',
    ])
  )
)

The new "identity function" should allow for syntax like:

      .where(List.entry<Person>().name, endsWith('ice')),

and

      .where(List.entry<Person>(), property('name', endsWith('ice'))),

Candidate names:

List.entry<T>()
List.item<T>()

[Dapangma]

I would rather name it List.item(), since you expect to have items in a List, while entries are expected from a dictionary (map).