Clearer documentation around the new generated bindings

lib/propolis-client/src/lib.rs

@@ -5,18 +5,33 @@
 //! which is opt-in at present with crate feature `generated`, and additional
 //! compatibility impls and re-exports to approximate the former handmade
 //! bindings' module layout with crate feature `generated-migration`.
+//!
+//! Presently, when built with the `generated` flag, the legacy handmade
+//! bindings are available in the `handmade` submodule.
+
+#![cfg_attr(
+    feature = "generated",
+    doc = "This documentation was built with the `generated` feature **on**."
+)]
+#![cfg_attr(
+    not(feature = "generated"),
+    doc = "This documentation was built with the `generated` feature **off**."
+)]
 
 pub mod instance_spec;
 
 #[cfg(feature = "generated")]
-pub mod generated;
-pub mod handmade;
+mod generated;
+#[cfg(feature = "generated")]
+pub use generated::*;
 
+#[cfg(feature = "generated")]
+pub mod handmade;
+#[cfg(not(feature = "generated"))]
+mod handmade;
 #[cfg(not(feature = "generated"))]
 pub use handmade::*;
 
-#[cfg(feature = "generated")]
-pub use generated::*;
 #[cfg(feature = "generated-migration")]
 pub use types as api;
 #[cfg(feature = "generated-migration")]