feature: share encoding versioning

[liamsi]

Summary

We may want to consider versioning the shares in order to allow for backwards-compatibility for on-chain smart contracts or programs that need to parse the shares but are not upgradeable.

originally posted by @musalbas on #757

Problem Definition

see above

Proposal

A version byte per share?

[liamsi]

I do think adding a byte on a per share level for very specific edge-cases is a optimizing for the wrong thing. But if this is a strict requirement, then yes, there is no way around this. If we already add some Meta Data to the share, we can actually look into putting this into CIDs instead as @Wondertan suggested.
Also I'd like to hear what @adlerjohn thinks about this.

[liamsi]

backwards-compatibility for on-chain smart contracts

@musalbas: smart contracts can be upgraded, right?

programs that need to parse the shares but are not upgradeable

Maybe we should not design our use of block space around other people's bad design decisions? What is a non-upgradeable program that we should care about for instance?

[musalbas]

@musalbas: smart contracts can be upgraded, right?

Not without hardforking unless they have upgrade keys (which everyone wants to avoid because that means the smart contract has a centralized point of failure)!

[adlerjohn]

It's not needed unless we plan on changing this after mainnet launch. Anything before then can be broken at will.

[musalbas]

Yes, we're talking about it possibly changing after mainnet.

[rootulp]

Safe to close this issue in favor of #839 ?

[rootulp]

Closing in favor of #839 and celestiaorg/celestia-app#659