- Delete src/credential.rs - module was unused in actual codebase
- Remove credential module references from lib.rs exports
- Update documentation to use standard OAuth2 terminology
- Fix CLI docs to reference correct credential_file config
- Application uses ConsoleApplicationSecret directly instead
The custom Credential struct duplicated functionality already
provided by yup_oauth2::ConsoleApplicationSecret. All credential
loading is handled by ClientConfig::new_from_configuration() which
uses the standard OAuth2 types.