[tre] add initial code management docs

[rkm]

EIDF Documentation Pull Request

Description

First pass at user documentation for the TRE Code Management service.

Type of change

Please delete options that are not relevant.

• Incorrect Documentation
• Incomplete Documentation
• Missing Documentation
• Formatting
• New Documentation

What has to be reviewed

All changed files.

Checklist

• Documentation follows the project style guidelines
• Ensure Contact details contain Service Emails and Numbers
• Self-review of documentation using mkdocs on local system
• Spellcheck has been performed
• Pre-commit has been run and passed

[2bPro]

Has this been decided, and is it something that we need to tell the users?

[rkm]

I've fixed this now, as the type of mirrororing discussed in the design is an egress from the TRE. The design didn't actually cover automatic ingress mirroring, though that would be a straightforward extension.