CDS credential parameters can't be passed to new_data_store

[pont-us]

When attempting to use the CDS store via the xcube.core.store.new_data_store method:

> cds = new_data_store('cds', endpoint_url='https://cds.climate.copernicus.eu/api/v2', cds_api_key='12345:abcd1234-1234-5678-abcd-123456789abc')

...
ValidationError: Additional properties are not allowed ('cds_api_key', 'endpoint_url' were unexpected)
...

However, these parameters do work when supplied directly to the CDSDataStore constructor.

[pont-us]

CDSDataStore.get_data_store_params_schema returns a schema which omits these parameters; they should be added to the schema.