RDS Upgrade Guide?

[jamiejackson]

Not really bug, but a question. (Alternatively, is there a mailing list or other forum for support?)

Is there a guide for using this module for upgrading RDS versions? I haven't dug in myself yet, but my team reports that in the process of importing an RDS instance into terraform (using this module), then doing an RDS upgrade via terraform:

The module tries to drop the old parameter group and create a new one. However, the old parameter group is attached to old snapshots and won't delete, which causes problems.

So, we're looking for a guide to using this module in the context of RDS upgrades. Failing that, we're looking for an approach to dealing with this parameter group issue, in particular.

My first thought would be to try a lifecycle prevent_destroy on the parameter group but currently, that can't be done from a module's caller.