bug: fix oidc exchange @mcalhoun (#1291)
## whatupdate viper config to read odic env vars
why
the env vars aren't currently bound the configuration, so they're not being read
Summary by CodeRabbit
- Chores
- Updated environment variable handling for GitHub OIDC token retrieval to improve configuration consistency.
- Simplified and enhanced tests related to GitHub OIDC token fetching and error handling.