Export policy bundles with metadata

Policy bundles must contain all information needed for the policy to operate when imported by another policy service instance. Additional data will be placed in a dynamically generated file named metadata.json.

Metadata will include:

• Policy repository, group, name and version
• DID public key reference like did:web:example.com#key1
• Policy last update date
• Policy locked/unlocked state
• Policy data refresh configuration

Bundle signing shall be implemented in a separate ticket #37 (closed)