message: Add consts for environment variables
diff: @@ -6,6 +6,9 @@ use serde::{Deserialize, Serialize};
  use crate::terminal::emoji;
  use config::{Config, Environment, File};
  +const CF_API_TOKEN: &str = "CF_API_TOKEN";
  +const CF_API_KEY: &str = "CF_API_KEY";
  +const CF_EMAIL: &str = "CF_EMAIL";
  #[derive(Clone, Debug, Deserialize, Serialize, PartialEq)]
  #[serde(untagged)]
  @@ -111,9 +114,9 @@ mod tests {
  // This test evaluates whether the GlobalUser returned is
  // a GlobalUser::TokenAuth (expected behavior; token
  // should be prioritized over email + global API key pair.)
  - env::set_var("CF_API_TOKEN", "foo");
  - env::set_var("CF_EMAIL", "test@cloudflare.com");
  - env::set_var("CF_API_KEY", "bar");
  + env::set_var(CF_API_TOKEN, "foo");
  + env::set_var(CF_EMAIL, "test@cloudflare.com");
  + env::set_var(CF_API_KEY, "bar");
  let user = GlobalUser::new().unwrap();
  assert_eq!(
  