Consider deprecating old validation API

**Feature request**
It would be great to have retry for middleware.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_retry` with default `false`.

Start by locating the middleware implementation and the configuration entry points in the repository. Check how existing middleware options are defined and tested, then determine what behavior and tests would establish that the enable_retry option works with its stated default.

Written by the indexing model from the issue text.