Share the platform-neutral Rust mobile contract (#91)

crates/storage/src/authentication.rs

@@ -55,6 +55,12 @@ pub trait AuthenticationClock: Send + Sync + 'static {
     fn now(&self) -> Duration;
 }
 
+impl<T: AuthenticationClock + ?Sized> AuthenticationClock for Arc<T> {
+    fn now(&self) -> Duration {
+        (**self).now()
+    }
+}
+
 /// Process-local monotonic clock used by production sessions.
 #[derive(Clone, Debug)]
 pub struct SystemAuthenticationClock {