Allow for configuring more Terraform aws options

At the moment there is no way for a user to configure any options in the terraform modules unless it is an option we have created a var for.

For example when creating an RDS instance there are a lot of options that we do not provide access to that someone might want to configure, not all options will be configurable after an instance is created.

We should decide if we want to allow access to configuring these options on an as needed basis, give guidance on how to add more options to the .tf files or just add vars for them ourselves.