As config settings it should be possible in the future to either take "default" setting or "custom_data" setting for the parameters
"default" setting --> pypsa-eur data
"custom_data" setting --> taking custom_data provided by the user using a csv-equivalent
When taking "custom_data" setting, it is possible to provide data on larger scale (e.g. Africa, West Africa, etc.), which gets seperated into the countries as already happening for example in the "countries" config setting with create_country_list()
Describe the feature you'd like to see