pinakes-server: fix session token generation to use manual charset

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I80848fad9272ea7c199b17124ce767ce6a6a6964

crates/pinakes-server/src/routes/auth.rs

@@ -73,11 +73,14 @@ pub async fn login(
     let user = user.expect("user should exist at this point");
 
     // Generate session token
-    use rand::Rng;
-    let token: String = rand::rng()
-        .sample_iter(&rand::distr::Alphanumeric)
-        .take(48)
-        .map(char::from)
+    let token: String = (0..48)
+        .map(|_| {
+            const CHARSET: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
+                                      abcdefghijklmnopqrstuvwxyz\
+                                      0123456789";
+            let idx = (rand::random::<u32>() as usize) % CHARSET.len();
+            CHARSET[idx] as char
+        })
         .collect();
 
     let role = user.role;