Accessing aws_db_subnet_group.this when its count = 0 is an error, so we
need to instead access it via splat syntax and then apply a default value
for when the resulting list is empty.

Added iam_database_authentication_enabled and license_model model

Added complete example for Postgres RDS

support final_snapshot_identifier

Update README

Add enhanced monitoring

Using `storage_encrypted` to set the db_instance.storage_encrypted

db parameters can now be passed to db_parameter_group module