Publish to temp directory

Description

In order to avoid conflicts with other publishing requests we will use a temporary directory containing the book repo for publishing. We will also use a temporary directory to publish to until the process is complete. This will avoid potentially taking down the guide if there is an error in the publishing process.

Before

A single directory was used to store the repo used in the mkdocs build process. Results were published directly to the web root.

After

The directory used by mkdocs is a temporary copy. Results are published to a temporary directory until they are ready.

• Tests pass