Add Connection::reset

There was an issue where the connection deque was referring to old arena memory

src/connection.cpp

@@ -118,10 +118,6 @@ bool Connection::writeBytes() {
   }
   assert(messages_.empty());
 
-  // Reset arena after completing request/response cycle
-  // This reclaims memory from request parsing and response generation
-  arena_.reset();
-
   return false;
 }
 

src/connection.hpp

@@ -52,6 +52,13 @@ struct Connection {
     return result;
   }
   void *user_data = nullptr;
+  void reset() {
+    assert(messages_.empty());
+    arena_.reset();
+    messages_ =
+        std::deque<std::string_view, ArenaStlAllocator<std::string_view>>{
+            ArenaStlAllocator<std::string_view>{&arena_}};
+  }
 
   // Note: To release connection back to server, use
   // Server::releaseBackToServer(std::move(connection_ptr))