Metadata argument

[rg5051]

Some functions such as ons_download() have a metadata argument but it's not clear immediately what this argument should be. It depends on calling monstr_pipeline_defaults() and ons_datasets_setup().

Is there a way to call ons_download() without using those earlier functions.
Could the documentation be clearer to tell users where the metadata argument comes from and what it should be?

[fiona-grimm]

Thanks Rob! @emmavestesson will pick this up once she's back.