Improve error messages in parsers

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

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

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

The issue names no files, tests, or entry points, and its title does not match the middleware notification request. Start by locating the middleware configuration and parser-related code, then determine how notification behavior is specified. Done should include a documented enable_notifications option with a default of false and defined notification behavior.

Written by the indexing model from the issue text.