Copying @paraseba's suggestion from pydata/xarray#10457:

Long term, I'd love to see the responsibility for managing the readonly flag removed from the abstract Store hierarchy. It feels this is a concern that is beyond what a Store should know about. It would help us keeping the Stores abstract and focused. Readonly-ness sounds like a session concern, independent of the details of how to write zarr objects to different media.

cc @maxrjones @d-v-b