Create a drush command that creates File and Media entities from unmanaged files on a remote filesystem.

Problem/Motivation

A frequent request is for users adopting Drupal that already have a plethora of files on a remote file system to be able to create Drupal’s required file_managed records and (if using Media) media entities from the remote files.

No Drupal migration is really necessary here, as the files are already physically stored on the remote instance, the updates that are needed are strictly Drupal internal.

Proposed resolution

This issue is for tracking the development of a drush command that can be executed that will, in batches of 2500 files (default value that can be overridden) at a time, read the files stored on the object store and create the necessary Drupal internal entities needed to fully manage those files with Drupal and the Flysystem module.

Remaining tasks

* Write the drush command
* Write tests for the drush command
* Update the README with usage documentation

User interface changes

None

API changes

None

Data model changes

Created file_managed records in existing Drupal tables, created Media Entities using those file records.