As a user, I want pulp-manage-db to output a message before any "known big migrations", so that I am aware that the migration could potentially be time-consuming
CLOSED - CURRENTRELEASE
This is related to #2059. For any long-running migrations in pulp-manage-db, it would be informative to have a simple message, e.g.
NOTE: This migration may take a long time depending on the size of your Pulp content. See pulpproject.org/123 for details.
The details link would be a bonus if there are any links to migration details.