der: impl RefToOwned/OwnedToRef for &[u8]/Box<[u8]> (#1188)

Signed-off-by: Arthur Gautier <[email protected]>

der/src/referenced.rs

@@ -45,3 +45,25 @@ where
         self.as_ref().map(|o| o.ref_to_owned())
     }
 }
+
+#[cfg(feature = "alloc")]
+mod allocating {
+    use super::{OwnedToRef, RefToOwned};
+    use alloc::boxed::Box;
+
+    impl<'a> RefToOwned<'a> for &'a [u8] {
+        type Owned = Box<[u8]>;
+
+        fn ref_to_owned(&self) -> Self::Owned {
+            Box::from(*self)
+        }
+    }
+
+    impl OwnedToRef for Box<[u8]> {
+        type Borrowed<'a> = &'a [u8];
+
+        fn owned_to_ref(&self) -> Self::Borrowed<'_> {
+            self.as_ref()
+        }
+    }
+}