Summary

Modify the current draft implementation of the DocLocator type to starting actually define it as ipfs Cid v1

Description

• Use ipld-core = { version = "0.4.1", features = ["serde"]} crate version
• Update the DocLocator to pub struct DocLocator(ipld_core::Cid);
• Modify the DocumentRef API, so it will start hashing the CatalystSignedDoc bytes and properly derive a DocLocaltor type

Additional notes

Note: Only CIDv1 with multihash sha2-256 is permitted for document CIDs; implementations MUST reject other multihash functions.

CIDv1 binary encoding

• Layout (packed bytes): cidv1 = varint(1) || varint(multicodec) || multihash.
• Multihash for this PoC MUST be sha2-256 with a 32-byte digest:
  • multihash = varint(0x12) || varint(32) || digest[32].
• Length varies slightly (36..40 bytes) due to varint encoding of the multicodec field.
• We do not accept other multihash functions.

References

• CIDv1 specification: https://github.com/multiformats/cid
• Multicodec table: https://github.com/multiformats/multicodec
• Multihash specification: https://github.com/multiformats/multihash