Fix 2FA Remember to actually be 30 days (#6929)

Currently we always regenerate the 2FA Remember token, and always send that back to the client.
This is not the correct way, and in turn causes the remember token to never expire.

While this might be convenient, it is not really safe.
This commit changes the 2FA Remember Tokens from random string to a JWT.
This JWT has a lifetime of 30 days and is validated per device & user combination.

This does mean that once this commit is merged, and users are using this version, all their remember tokens will be invalidated.
From my point of view this isn't a bad thing, since those tokens should have expired already.

Only users who recently checked the remember checkbox within 30 days have to login again, but that is a minor inconvenience I think.

Signed-off-by: BlackDex <black.dex@gmail.com>

src/db/models/device.rs

@@ -1,6 +1,6 @@
 use chrono::{NaiveDateTime, Utc};
 
-use data_encoding::{BASE64, BASE64URL};
+use data_encoding::BASE64URL;
 use derive_more::{Display, From};
 use serde_json::Value;
 
@@ -67,10 +67,13 @@ impl Device {
     }
 
     pub fn refresh_twofactor_remember(&mut self) -> String {
-        let twofactor_remember = crypto::encode_random_bytes::<180>(&BASE64);
-        self.twofactor_remember = Some(twofactor_remember.clone());
+        use crate::auth::{encode_jwt, generate_2fa_remember_claims};
 
-        twofactor_remember
+        let two_factor_remember_claim = generate_2fa_remember_claims(self.uuid.clone(), self.user_uuid.clone());
+        let two_factor_remember_string = encode_jwt(&two_factor_remember_claim);
+        self.twofactor_remember = Some(two_factor_remember_string.clone());
+
+        two_factor_remember_string
     }
 
     pub fn delete_twofactor_remember(&mut self) {