Simplify user token generation

src/auth.rs

@@ -3,7 +3,10 @@ use std::sync::Arc;
 use base64::{prelude::BASE64_STANDARD, Engine};
 use hmac::{Hmac, Mac};
 use md5::Md5;
-use rand::{seq::IteratorRandom, thread_rng};
+use rand::{
+    distributions::{Alphanumeric, DistString},
+    thread_rng,
+};
 use secrecy::{ExposeSecret, SecretVec};
 use thiserror::Error;
 use time::{macros::format_description, OffsetDateTime};
@@ -33,22 +36,16 @@ pub struct Authenticator {
 }
 
 impl Authenticator {
+    const USER_TOKEN_LEN: usize = 30;
+
     pub fn new(db: Arc<Mutex<SqliteDatabase>>) -> Self {
         Self { db }
     }
 
     #[instrument]
     pub async fn create_user_token(&mut self, username: &str, password: &Password) -> UserToken {
-        let mut token_str = "".to_owned();
-
-        let mut rng = thread_rng();
-        for _ in 0..30 {
-            let digit = (0..=15).choose(&mut rng).unwrap();
-            let char = (('a' as u8) + digit) as char;
-            token_str.push(char)
-        }
-
-        let new_token = UserToken::from(token_str);
+        let new_token =
+            UserToken::from(Alphanumeric.sample_string(&mut thread_rng(), Self::USER_TOKEN_LEN));
 
         let mut db = self.db.lock().await;
         if let Err(err) = db.save_token(username, &new_token).await {