Document the self-code ingress feature

[cptanalatriste]

✅ Checklist

• I have searched open and closed issues for duplicates
• This is a request for a change to documentation
• This isn't a feature request or bug report
• This isn't an open-ended question (open a discussion if it is).

📒 Where is the problem?

The new self-code ingress feature is not documented (see: #2482)

📝 Required documentation changes

Describe the new config file structure and the requirements for ingressing code.