Goal: 

• Snapshots older than a configured time should be automatically deleted. This can happen during nightly-jobs, which already runs periodically. In the template response for list and/or fetch, a list of UUIDs of soon-to-expire snapshots be returned. This is to support the UI alerting the user of soon-to-be-impacted templates.
• Custom, Red Hat, & Upload repositories should be considered to have snapshots deleted

Acceptance Criteria:

• A new environment variable should be used to configure a time for snapshots to be deleted. 365 days for prod, 90 days for stage.
• A cleanup should run during nightly-jobs that deletes all snapshots older than the configured time. 
• Templates associated with deleted snapshots should automatically be updated to used the next available snapshot.
• A snapshot should never be deleted if it is the last snapshot in the repository.
• The template response should include UUIDs of associated snapshots that expire in the next week ( ...?) . 
• As part of the template response, return a list of snapshots with repo information that are going to be deleted soon.