Support Datastore-API as an alternative to IDS #32
Description
Work on the Facilities Data Pipeline for EPAC will involve a new component in place of the IDS. Requests that are send to the IDS currently by DataGateway and DataGateway Download API should also have the option to go to this new component.
In practice, this will mean creating a new FtsClient (alongside the current IdsClient) and making the choice a config option. Other changes or generalisations may also be needed.