fix: rds bootstrap

[aliziel]

Summary:

Addresses issues surfaced during initial stack create on EIC:

• Syntax error in bootstrapper SQL command to create non-superuser
• Rollback failure on RDS-dependent resources

Changes

• SQL syntax error
  • Reverted Identifier use on non-identifier parameters
  • Break up command + use one role exists check
    • Identifier use caught the CREATE USER condition in update command
• Rollback failure
  • Make deletion protection configurable, defaulting to True
    • Useful for other database maintenance procedures
  • Allow database rollback on failed create with RETAIN_ON_UPDATE_OR_DELETE

PR Checklist

• Unit tests
• Ad-hoc testing - Deploy changes and test manually
• Integration tests
• Infrastructure changes - test using terraform validate and terraform plan

[aliziel]

Wanted to note previous concern about parameter binding + injection.

Both .format() and %s look like Python-based string interpolation (unsafe), but these are psycopg methods:

• This version mirrors an example in their .format() documentation that includes both identifiers and literals
• We can also blend with psycopg serverside parameters, if preferred (see last example in linked section)