Displaying obsolete geographies on maps/charts

[bothness]

Some datasets have both new and old geography codes (including for merged unitaries and boundary changes).

We need a robust rule that ensures that we don't show duplicate areas on maps/charts, and that maps don't include both merged and unmerged areas at once.

Agreed with the business area that we'd follow the rule that we only map areas in the original source datasets, with the exception of combined authorities. Charts may potentially include both merged and unmerged areas.

[bothness]

Look at Sheffield/Barnsley for population indicators. Gap on map.

[Shiny-Penny]

Does this one include this issue from the log: "When on a region indicator page, you can change the 'Related area group' (via 'Change areas' button). It gives an option for upper tier/UA in region and lower tier/UA in region, however nothing changes on the charts between these two options. Therefore, does it make sense to only keep one of the options?"

--- Ignore this. Located #150