docs: add additional requirements for schema

Author: Dr-Emann

src/ffi/context.rs

@@ -19,6 +19,7 @@ use uuid::fmt::Hyphenated;
 /// Violating any of the following constraints will result in undefined behavior:
 ///
 /// - `schema` must be a valid pointer returned by [`schema_new`].
+/// - `schema` must be alive, and unmodified at least until [`context_free`] is called on the result
 ///
 /// [`schema_new`]: crate::ffi::schema::schema_new
 #[no_mangle]

src/ffi/router.rs

@@ -23,6 +23,7 @@ use uuid::Uuid;
 /// Violating any of the following constraints will result in undefined behavior:
 ///
 /// - `schema` must be a valid pointer returned by [`schema_new`].
+/// - `schema` must be alive, and unmodified at least until [`router_free`] is called on the result
 ///
 /// [`schema_new`]: crate::ffi::schema::schema_new
 #[no_mangle]