registry: grant metadata

[mds1]

We don't currently have requirements/specs for metadata, but considerations include:

• On-chain metadata validation like EIP-3668
• Develop a JSON schema that all grants must follow
• How to version metadata, especially in the context of curation (e.g. preventing a grant from entirely changing their description after approval). First pass of ideas:
  • Require an on-chain transaction to store a timestamp of last update on-chain?
  • Store a hash of metadata somewhere?
  • Move to curation layer somehow?
• Users should not be limited to one protocol, e.g. IPFS, and should be able to use the service of their choice (potentially including centralized ones like AWS S3)
• Check any implementations across a variety of file storage protocols such as IPFS, Arweave, Storj, etc