The Postgres Instance template is a collection of files to create an RDS instance. You shoud copy it, edit it and
check it in a separate repository.
It also install a cloudformation custom resource to manage individual databases on the instance itself.
Here is the list of configurable options:
Instance Identifier: the Instance Identifier is configured in the postgresInstance.sh shell script via
the env var DATABASE_INSTANCE_NAME
VPC: the VPC for the RDS instance is configured in the postgresInstance.sh shell script via the env var VPC_ID.
Per default, the RDS is created in the default VPC.
Storage/Machine/etc.. : in the template postgresInstance.yaml on the resource Instance directly.