Add copying utility methods to Arena

src/commit_request.hpp

@@ -244,14 +244,7 @@ public:
    * @return String view pointing to arena-allocated memory
    */
   std::string_view copy_to_arena(std::string_view str) {
-    if (str.empty()) {
-      return {};
-    }
-
-    char *arena_str = arena_.allocate<char>(str.size());
-    std::memcpy(arena_str, str.data(), str.size());
-
-    return std::string_view(arena_str, str.size());
+    return arena_.copy_string(str);
   }
 
   /**