ENG-14270: redshift iam

Description of the change

We recently added the capability for Redshift repos to use AWS IAM as the Authentication method between the sidecar and the DB. In order to do this, we added a few fields to the repo and the userAccount objects, so this PR teaches Terraform about them.

Type of change

[ ] Bug fix (non-breaking change that fixes an issue)
[ ] New feature (non-breaking change that adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklists

Development

[ ] Lint rules pass locally
[ ] The code changed/added as part of this pull request has been covered with tests
[ ] All tests related to the changed code pass in development

Code review

[ ] This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
[ ] Jira issue referenced in commit message and/or PR title

Testing

Added a couple new unit tests and they passed.

cyralinc / terraform-provider-cyral

ENG-14270: redshift iam #559