Update to runbook

[kal]

Due to major changes in the repository it was easier to open a new PR than to try and update #169

Changes since the last version of the document

• Listed out other downstream dependencies
• Removed the task to move the model to a separate repository as that is now done
• Include consideration of the new staging-dev environment and how this could be used to manage the roll-out of model changes
• Document the types of model change that could be considered breaking vs non-breaking.

[der]

Looks good to me.

Having a dev environment for dependent services certainly makes sense, if it can be done.