restore the extract function for server functions (#4849)

* restore the extract function for server functions

* fix compilation

* Move most fields under one shared lock

* fix typo

* fix clippy

* restore somewhat misleading FromRequest bound

* remove unused import

* fix doc links

Cargo.lock

@@ -5861,9 +5861,11 @@ dependencies = [
  "generational-box",
  "http 1.3.1",
  "inventory",
+ "parking_lot",
  "serde",
  "serde_json",
  "thiserror 2.0.17",
+ "tokio",
  "tracing",
 ]