A few comments on rust walproposer build.

libs/walproposer/build.rs

@@ -1,3 +1,6 @@
+//! Links with walproposer, pgcommon, pgport and runs bindgen on walproposer.h
+//! to generate Rust bindings for it.
+
 use std::{env, path::PathBuf, process::Command};
 
 use anyhow::{anyhow, Context};

libs/walproposer/src/api_bindings.rs

@@ -1,3 +1,6 @@
+//! A C-Rust shim: defines implementation of C walproposer API, assuming wp
+//! callback_data stores Box to some Rust implementation.
+
 #![allow(dead_code)]
 
 use std::ffi::CStr;