Handle edge cases in notifications

**Feature request**
It would be great to have backup for routes.

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

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

No files, tests, or entry points are named. Start by locating where route handling and configuration options are defined, then determine what “backup for routes” means and how enable_backup should affect production deployments. Done should include a defined fallback behavior and coverage for the option's default and enabled cases.

Written by the indexing model from the issue text.