Rename DefaultAuthorizedUser to ConfigDefaultCredentials

I found it hard to intuitively tell the difference between
DefaultAuthorizedUser and DefaultServiceAccount.

src/authentication_manager.rs

@@ -2,7 +2,7 @@ use async_trait::async_trait;
 use tokio::sync::Mutex;
 
 use crate::custom_service_account::CustomServiceAccount;
-use crate::default_authorized_user::DefaultAuthorizedUser;
+use crate::default_authorized_user::ConfigDefaultCredentials;
 use crate::default_service_account::DefaultServiceAccount;
 use crate::error::Error;
 use crate::gcloud_authorized_user::GCloudAuthorizedUser;
@@ -48,9 +48,9 @@ impl AuthenticationManager {
         }
 
         let client = types::client();
-        let default_user_error = match DefaultAuthorizedUser::new(&client).await {
+        let default_user_error = match ConfigDefaultCredentials::new(&client).await {
             Ok(service_account) => {
-                tracing::debug!("Using DefaultAuthorizedUser");
+                tracing::debug!("Using ConfigDefaultCredentials");
                 return Ok(Self::build(client, service_account));
             }
             Err(e) => e,

src/default_authorized_user.rs

@@ -12,12 +12,12 @@ use crate::types::{HyperClient, Token};
 use crate::util::HyperExt;
 
 #[derive(Debug)]
-pub(crate) struct DefaultAuthorizedUser {
+pub(crate) struct ConfigDefaultCredentials {
     token: RwLock<Token>,
     credentials: UserCredentials,
 }
 
-impl DefaultAuthorizedUser {
+impl ConfigDefaultCredentials {
     const DEFAULT_TOKEN_GCP_URI: &'static str = "https://accounts.google.com/o/oauth2/token";
     const USER_CREDENTIALS_PATH: &'static str =
         ".config/gcloud/application_default_credentials.json";
@@ -77,7 +77,7 @@ impl DefaultAuthorizedUser {
 }
 
 #[async_trait]
-impl ServiceAccount for DefaultAuthorizedUser {
+impl ServiceAccount for ConfigDefaultCredentials {
     async fn project_id(&self, _: &HyperClient) -> Result<String, Error> {
         self.credentials
             .quota_project_id