[tik65536]

Summary

• A collection provider supports the xdggs-plugin for DGGS datasets stored in Zarr using the xarray Datatree as an accessor.
• The implementation is based on xdggs 0.7.0

Implementation summary

• XdggsCollectionProvider inherits from ZarrCollectionProvider
• They differ in initialisation and in part of the get_data method because xarray-sql doesn't support xindexes
• All datasets are instantiated with the xdggs index at start, together with xarray indexing options (i.e. range index, moc inde)
• As mentioned above, xarray-sql is not compatible with xdggs, so when CQL is used in zone_query or zone_data_retrieval, the get_data function of XdggsCollectionProvider has to drop the xdggs index before it continues to the parent's get_data method. After the query is done, it restores the dataset with the xdggs index.
• It doesn't require the user to specify the mapping between groups and refinement levels; those are retrieved from the xdggs dataset attributes.