Issue: Tables are left scaled up after stack deletion. We have banners in the lab explaining the importance of deleting DDB tables, but these aren't foolproof.

Recommended resolution:

• 1. Tables in the hands on python labs are tagged on creation
• 2. We should create a CFN custom resource or similar that blocks stack deletion if the DDB tables are not cleaned up
• 3. We should send an error message in the stack events if the tables still exist, and return a hyperlink to AWS resource manager to review the list of tables and clean them up