Maintain, secure, and upgrade

This was once a long page covering a bunch of topics; those topics have since all moved to dedicated pages:

Monitoring

Moved to Troubleshooting.

Securing your Zulip server

Moved to Security model.

Upgrading

Moved to Upgrading to a release.

Upgrading from a Git repository

Moved to Upgrading from a Git repository.

Upgrading the operating system

Moved to Upgrading the operating system.

Scalability

Moved to Scalability.

Management commands

Moved to Management commands.

API and your Zulip URL

Moved to REST API.