Add ability to use Objectionjs Graph Upsert for the create method

[NotAmaan]

The graphUpsert offered by objection.js can also be used to insert data. It offers more flexibility when creating multiple records or relationships.

Example use-case:

const data = [{
  id: 'movie-one',
  name: 'Movie One',
}, {
  id: 'movie-two',
  name: 'Movie Two'
}];

A movie with the id movie-two already exists.

Create request:
app.service('movies').create(data)

Response if using insert graph:
Error: id provided has already been used

Response if using upsert graph:

[{
  id: 'movie-one',
  name: 'Movie One',
  createdAt: '2018-09-10T15:03:54.929Z',
  updatedAt: '2018-09-10T15:03:54.930Z'
}, {
  id: 'movie-two',
  name: 'Movie Two',
  updatedAt: '2018-09-10T15:03:54.940Z'
}]

This is just one of the many use-cases as it can also be used for relationships.

Suggested API:
A new option called createUseUpsertGraph