Appease Clippy 1.68 and refactor http_api (#4068)

## Proposed Changes

Two tiny updates to satisfy Clippy 1.68

Plus refactoring of the `http_api` into less complex types so the compiler can chew and digest them more easily.

Co-authored-by: Michael Sproul <michael@sigmaprime.io>

common/compare_fields_derive/src/lib.rs

@@ -1,4 +1,3 @@
-#![recursion_limit = "256"]
 extern crate proc_macro;
 
 use proc_macro::TokenStream;