Splits the auto-response declaration and response body into two separ…

…ate steps

openapi.go

@@ -189,11 +189,18 @@ func RegisterOpenAPIOperation[T, B any](s *Server, route Route[T, B]) (*openapi3
 	}
 
 	// Automatically add non-declared 200 Response
-	if route.Operation.Responses.Value("200") == nil {
+	response200 := route.Operation.Responses.Value("200")
+	if response200 == nil {
+		response := openapi3.NewResponse().WithDescription("OK")
+		route.Operation.AddResponse(200, response)
+		response200 = route.Operation.Responses.Value("200")
+	}
+
+	// Automatically add non-declared Content for 200 Response
+	if response200.Value.Content == nil {
 		responseSchema := SchemaTagFromType(s, *new(T))
 		content := openapi3.NewContentWithSchemaRef(&responseSchema.SchemaRef, []string{"application/json", "application/xml"})
-		response := openapi3.NewResponse().WithDescription("OK").WithContent(content)
-		route.Operation.AddResponse(200, response)
+		response200.Value.WithContent(content)
 	}
 
 	// Automatically add non-declared Path parameters