Harmonising the addition of measurement metadata to stac_discovery #304

"reflectance": {
          "href": "/measurements/reflectance",
          "type": "application/vnd.zarr; version=3; profile=multiscales",
          "title": "Surface Reflectance",
          "roles": [
            "data",
            "reflectance"
          ],
          "gsd": 10,
          "proj:code": "EPSG:32633",
          "proj:shape": [
            10980,
            10980
          ]
        }

class Product(StrEnum):
    _product = "L1C" # ... or anything else

    @classmethod
    def from_filename(cls, filename: str | None) -> S2Type | None:
        if not filename:
            return None
        for member in cls:
            if member.value in filename:
                return member
        return None

    @classmethod
    def from_datatree(cls, dt: xr.DataTree) -> S2Type | None:
        """Product level from `stac_discovery` `product:type`, else from the tree name.

        A tree opened from a Zarr store has no name, so the name alone is not enough.
        """
        return cls.from_filename(product_type_of(dt)) or cls.from_filename(dt.name)

DATA_PRODUCT = Product.from_datatree(dt_input)

for group_path in datasets:
        # extract all the parent paths and names
        parent, _, name = group_path.rstrip("/").rpartition("/")
        if parent not in datasets:
            init_zarr_group(output_path + group_path)

        # consolidate all measurement groups
        if name == "measurements":
            assign_stac_discovery_thing(...)
            zarr.consolidate_metadata(output_path + group_path, zarr_format=ZARR_FORMAT)