Technical helper module to copy file / image field data to an existing Drupal Core Media field in the same entity / entities.

Only for developers, no production use!

Condition:

You have an entity type with a regular file / image field (non-media), for example from a migration and you want to migrate it into a media field.
The media field already exists and is empty or has to be created before using this module. It should never have any values yet.

You do not want to use heavy weight migration.