healpix-geo dggrs provider

[tik65536]

• Added healpix dggrs (healpixgeo_dggrs_provider.py) with nested and zuniq indexing using healpix-geo

  • Implementation based on healpix-geo v0.4.1
  • HealpixGeoNestedProvider
    • The implementation is based on the discussion from OGC API-DGGS
    • The textual ZIRS of the nested index is in the form of "{refinement_level}_{nested_cell_id}", the refinement level is a 2-digit string with a 0 prefix.
    • The implementation is tested with ZarrCollectionProvider, as the datatree stores different refinement levels as different datasets.
  • HealpixGeoZuniqProvider
    • zuniq doesn't come with the textual ZIRS representation at the moment of implementation, so I treat the string version of cell ID as the textual ZIRS.
    • Support conversion to nested indexed collections, which means collections with nested index can be queried using the zuniq index.

• Changed to use shapely.geometry.shape instead of shapely.from_geojson to create shapely polygons.

• TilesAPI support conversion between dggrsid with query parameter?dggrsid=<dggrsid>

• Notes on implementations:

  • I didn't use the healpix-geo auto module due to it requiring a grid object that is a frozen data class with refinement level specified for nested index. That means that when the refinement level changes, I have to create another object. It is not suitable for API purposes, where the refinement level often changes in the query, and for multi-refinement-level collections.