S3FileAdapter for static file uploads

[jesstelford]

Feature request

how to hook up their static app/File field to a cloud provider for file storage (e.g AWS s3?)
(from Slack)

Describe the solution you'd like

A new file storage adapter which allows me to save & retrieve files directly to/from an S3 bucket.

Something like;

const { File } = require('@keystonejs/fields');
const { S3FileAdapter } = require('@keystonejs/file-adapters');

const fileAdapter = new S3FileAdapter({
  /*...config */
});

keystone.createList('Applicant', {
  fields: {
    file: {
      type: File,
      adapter: fileAdapter,
      isRequired: true,
    },
  },
});

The implementation of S3FileAdapter should follow the patterns of CloudinaryFileAdapter: https://github.com/keystonejs/keystone/blob/master/packages/file-adapters/lib/cloudinary.js

[LiamAttClarke]

#1986

[Vultraz]

Can be closed now.