KeystoneJS S3 Storage Adapter

S3-based storage adapter for KeystoneJS (v2.0.0). Designed to replace the existing S3File field using the new storage API. Provides persistent file storage on Amazon S3 with configurable bucket, region, path, custom public URLs, and upload parameters. Supports per-file schema fields for bucket, path, etag, and URL. Release cadence is low/maintenance; this package is stable but tied to the older KeystoneJS stack (not Keystone Next). Alternatives include multer-s3 or direct S3 SDK, but this integrates directly with Keystone's file field system.