- Add `define_cli_auth_test!` macro for authentication-required tests
- Add `define_cli_list_test!` macro for unauthenticated list tests
- Replace 18 auth tests and 5 list tests with macro invocations
- Add `create_entity_cli()` generic, convert per-entity helpers to
thin wrappers
- Move `create_bag` and `create_gear` from brews_cli.rs to helpers.rs
