refactor(server): added SafeCell abstraction for easier protected memory swap

server/crates/arbiter-server/tests/common/mod.rs

@@ -1,19 +1,18 @@
 use arbiter_proto::transport::{Bi, Error};
 use arbiter_server::{
     actors::keyholder::KeyHolder,
-    db::{self, schema},
+    db::{self, schema}, safe_cell::{SafeCell, SafeCellHandle as _},
 };
 use async_trait::async_trait;
 use diesel::QueryDsl;
 use diesel_async::RunQueryDsl;
-use memsafe::MemSafe;
 use tokio::sync::mpsc;
 
 #[allow(dead_code)]
 pub async fn bootstrapped_keyholder(db: &db::DatabasePool) -> KeyHolder {
     let mut actor = KeyHolder::new(db.clone()).await.unwrap();
     actor
-        .bootstrap(MemSafe::new(b"test-seal-key".to_vec()).unwrap())
+        .bootstrap(SafeCell::new(b"test-seal-key".to_vec()))
         .await
         .unwrap();
     actor