Import/Export for Statistics

[anvabr]

Problem description

#3336 brought the ability to configure and publish Statistics which users can use to assess the data from multiple documents. Currently these statistics, while being published, cannot be brought into another Guardian instance except for manually replicating them via the Statistics creation UI.

Requirements

Introduce an import/export capability into Guardian such that authorised users would be able to 'bring' 3rd-party created statistics from IPFS or files into their Guardian instance.

Definition of done

Import/export capability for Statistics exists in the Guardian, similar to that of policies and schemas.

Acceptance criteria

Users can import published statistics and use them in their Guardian instance.