Delete stage regression content

Issue

A large amount of end-to-end regression tests will be run on stage to:

push usage on stage to something close to production. This will better replicate the fail conditions that do not normally show upr with the light lode normally seen on these servers
allow testing of more regression content for unusual but occurring content in production.

These tests will generate a large amount of content that will require periodic and on-going deletion.

Specific content collection(s) used for this content:

guarantee that non-load content is protected
allow differentiation for secondary services:
- replic - control external duplication of this content
- audit - specifically identify to possibly bypass audit of this content

This content will most likely be created on an ongoing basis (e.g. triggered daily or more frequently)

Deletion should occur regularly to prevent content of a certain age from remaining on the system.

Validation checks to confirm that content has successfully been removed form both storage and inv db is critical

periodic cron job will run and trigger the deletion process
identify the content to be written by noting all inv db content remaining after a specific date (collection will help in this process)
ark lists for deletion will be automatically saved as delete ark lists used in deletion process
background deletions will be run preserving pid
- multiple deletions can be run concurrently if needed - may require tweaking to prevent overlap of content
- tuning will be critical
use inv_tasks to confirm completion of run

Note this process should self correct if deletion is failed.