Support monitoring configuration

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

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

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

The issue names no files, tests, or entry points. Start by locating the middleware configuration and existing configuration tests, then trace how middleware options are loaded; done means an enable_monitoring option exists and defaults to false, with coverage for that default.

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