vault's terraform approle doesnt need to access all of these kubernetes
roles, it was just added as a placeholder and access to the kubernetes
roles was via the `vault_admin` to-much-access account. this is an
effort to roll back that and make access more targeted.
- add kubernetes* ldap groups for specific cluster/role combinations
- remove tf_vault from kubernetes* roles
- migrate from individual terraform files to config-driven terragrunt module structure
- add vault_cluster module with config discovery system
- replace individual .tf files with centralized config.hcl
- restructure auth and secret backends as configurable modules
- move auth roles and secret backends to yaml-based configuration
- convert policies from .hcl to .yaml format, add rules/auth definition
- add pre-commit hooks for yaml formatting and file cleanup
- add terragrunt cache to gitignore
- update makefile with terragrunt commands and format target
