Ensure compatability with cardano-metadata-submitter

[sevanspowell]

Ensure the PR validator accepts the data the cardano-metadata-submitter creates.

[swagendorp]

This schema specification appears to be missing the required 'policy' field as defined in cardano-metadata-submitter

https://github.com/input-output-hk/metadata-server/blob/master/specifications/wallet/submission-schema.json

Does it need to be updated or does the wallet work with a subset of fields generated by cardano-metadata-submitter ?

[sevanspowell]

@swagendorp I believe I've brought the openapi specification up-to-date now: https://input-output-hk.github.io/offchain-metadata-tools/api/latest/#tag/query