Add support for simulations to report multiple regions

[steven-cd]

Currently, the output schema only supports models returning information for the exact region that was requested. However, WSS (and possibly covid19uk) will actually produce results at a lower granularity as well (e.g. a simulation for England will produce an overall result as well as results for individual regions within that) but these get thrown away.

It could be useful to be able to display these results, to reduce the work users have to do if they want to do subregion-level simulations. Interestingly, despite this not being part of the schema, sample data used in the web-ui actually did contain this, but it has now been corrected. This does give an example of how we can adapt the schema, but the potentially more complicated problem is:

• how do we adapt the web-ui?
• how should we handle cases where some of the models can produce results for sub-regions, but others can't?

[steven-cd]

Discussed during meeting that this can rapidly get very complicated. GitHub tried to add some support for this in the model.yaml file but it rapidly gets very complicated - geographic slicing does not have a lot of consistency. Juniper and CrystalCast may have some input into this.