New feature branch: model-migration

[Tim Penhey]

Just a heads up on a new feature branch.

This is the target branch for the new model migration work.

There is also a separate feature branch for machine-dep-engine which is
the focus of moving the machine agent to use the dependency engine,
which model migration will depend on.

The machine agent work can land independently of the model migration
which is why it has its own feature branch.

Cheers,
Tim