Improve core performance

**Feature request**
It would be great to have encryption for handlers.

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

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

Start by locating the handler entry points and the existing configuration parsing used by the project. Clarify what handler data must be encrypted, how keys are supplied and stored, and which production deployments are in scope before implementation. Done means the `enable_encryption` option defaults to `false`, encryption behavior is defined and tested, and existing deployments remain compatible.

Written by the indexing model from the issue text.