Add configuration options for encryption

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

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

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

Start by locating the middleware and existing configuration options in the Shell-based terminal agent. Clarify whether the requested work is encryption configuration or a middleware timeout, then define how enable_timeout behaves when false and how timeout values are supplied; done means the selected behavior is configured and covered by the relevant existing checks.

Written by the indexing model from the issue text.