Add Storage and UpgradeStorage to Env

src/api/mod.rs

@@ -0,0 +1,6 @@
+//! APIs for the environment.
+//!
+//! The [environment](crate::env::Env) is split into components. Each component has an API described
+//! by a trait. This module gathers the API of those components.
+
+pub mod upgrade_storage;