Type Alias HeaderMatcher 

pub type HeaderMatcher = Arc<dyn Fn(&str) -> Option<String> + Send + Sync>;

A handler for matching and transforming headers.

It takes a header name (as a string slice) and returns an Option<String>.

• Some(new_name): Renames the header to new_name (or keeps it if identical).
• None: Removes the header.

Aliased Type

pub struct HeaderMatcher { /* private fields */ }