PLT-1750 Demo Database Migration

[mianava]

🎫 Ticket

PLT-1750

🛠 Changes

Runs a database migration to add a user for running migrations using Database Iam via GitHub actions.

Runs a bootstrap to add this user. Models what a IAM policy looks like for adding a database user based on your own GRANTS in sql.

ℹ️ Context

🧪 Validation

These changes were applied from a git workflow dispatch of tofu-apply, and the database confirms:

postgres=> SELECT rolname, rolcanlogin FROM pg_roles WHERE rolname IN ('tftesting_migrator', 'tftesting_human');
      rolname       | rolcanlogin 
--------------------+-------------
 tftesting_migrator | t
(1 row)