Update ERC-8048: Make the metadata authority collection-wide - #2174

Remove holderCanWrite from the Collection Authority extension, so collectionAuthority() returns the authority and the lock, and CollectionAuthorityUpdated carries the same two values. Add the optional Holder Metadata extension, with canHolderUpdateMetadata(), the HolderCanUpdateMetadataSet event and ERC-165 interface ID 0x12c220bd. Add the rules for a contract that implements both extensions, and update the common setups, the house example, the reference implementation, the Rationale and the Security Considerations.

collectionAuthority() returns the authority alone and CollectionAuthorityUpdated carries the authority alone. Remove authorityLocked and every rule about who can change the authority or the holder flag from the Specification, and say that both are up to the implementation. Keep the lock in the reference implementation as an example, move the common setups table next to it, and adjust the house example, the Rationale and the Security Considerations.

Add one sentence to the Marketplace compatibility paragraph of the agent profile, telling clients to read canHolderUpdateMetadata() and collectionAuthority().

Replace the Holder writes text. A true flag now warns that an account that holds a token, or that a holder approved, can write its metadata. For ERC-721 the owner must be able to write, and approved addresses and operators are allowed. Make the Collection Authority exception, the rules for contracts with both extensions, the Rationale, the Security Considerations and the reference implementation comments consistent with it.

Remove the Holder Metadata extension and the section for contracts that implement both extensions. With a nonzero collection authority only the authority can write, with no exception, and holder writes are left to implementations. Move the house example under the Collection Authority extension, point the Marketplace compatibility sentence to collectionAuthority() only, and shorten the Rationale, the Security Considerations and the reference implementation to match.

… smallest change

Return to the upstream Optional Metadata Authority Extension and change only what makes it collection wide. The read is tokenMetadataAuthority(), the event is TokenMetadataAuthoritySet(address), the interface is IERC8048TokenMetadataAuthority and the ERC-165 ID is 0x04f90b41. A nonzero authority is the only address that can write, for every token. Remove the Collection Authority extension, the setups table and the lock added earlier on this branch. The reference implementation makes the collection owner the authority by default.