Migrate user_delete_request from Drupal

As part of the migration from Drupal 7, the user_delete_request feature will be added to the profile-api. This issue will be used as a place to generate discussion and gather requirements.

As I am still rather unfamiliar with this process/workflow, @cguindon is there a spec I can reference for this? Can you point me to where the current Drupal implementation is?