batching a model over multiplle extents via some command-line tool

[olliethomas]

This needs thinking about a bit.
A question: should this execute on the server or a local machine?

If on the server, then we need to make it an api endpoint.
If locally then we can either cobble together a headless browser than interacts with the app on your behalf... This would be brittle though. Or, could download the data and the model and execute locally.