Extra functionality for the User/Location groups implementation

[devsjc]

Moving some notes from Peter into a discussion here around the User/Location groups:

Various site/location group configurations that we currently have are here

Some extra things that we currently have:

• A location group for api checks. The airflow pulls some sites and then runs checks on these, like is there a forecast? Some sites we might want to keep the history of, some sites we are happy to through away

Would be nice (future):

• I can imagine the the future it would be nice to say: give me all the GSPs in the UK. Or give me all the GSPs in this one DNO a user having dafult access to UK forecast, but not other european forecasts