Refactor users management

* Shard `src/data/user.rs` into two different files
  * One for user data structure (same file)
  * One for user manipulation (new file: `user_file_entity.rs`)
* Isolate password hashing and verification

src/controllers/settings_controller.rs

@@ -103,7 +103,14 @@ pub async fn change_password_route(
         );
     } else if let Some(req) = req {
         // Invalid password
-        if !user.verify_password(&req.old_pass) {
+        if !users
+            .send(users_actor::VerifyUserPasswordRequest(
+                user.uid.clone(),
+                req.old_pass.clone(),
+            ))
+            .await
+            .unwrap()
+        {
             danger = Some("Old password is invalid!".to_string());
             bruteforce
                 .send(bruteforce_actor::RecordFailedAttempt {