Add From impl for header map references

actix-http/src/header/map.rs

@@ -643,6 +643,15 @@ impl From<http::HeaderMap> for HeaderMap {
     }
 }
 
+impl<T> From<&T> for HeaderMap
+where
+    T: Into<http::HeaderMap>,
+{
+    fn from(map: &T) -> Self {
+        map.to_owned().into()
+    }
+}
+
 /// Convert our `HeaderMap` to a `http::HeaderMap`.
 impl From<HeaderMap> for http::HeaderMap {
     fn from(map: HeaderMap) -> Self {
@@ -650,6 +659,13 @@ impl From<HeaderMap> for http::HeaderMap {
     }
 }
 
+/// Convert our `&HeaderMap` to a `http::HeaderMap`.
+impl From<&HeaderMap> for http::HeaderMap {
+    fn from(map: &HeaderMap) -> Self {
+        map.to_owned().into()
+    }
+}
+
 /// Iterator over removed, owned values with the same associated name.
 ///
 /// Returned from methods that remove or replace items. See [`HeaderMap::insert`]