versioning

[imabdulbasit]

This PR:

• moves types from the sequencer crate
• Moved SeqTypes to the types crate.
• implements all the hotshot traits for the SeqTypes
• moves all the helper functions, types and some traits needed for hotshot trait implementations or types
• creates a versioned Header type in v0/header.rs and the serialization/deserialization

things to review:

• v0/header.rs
• Serialization and test_versioned_header_serialization() in v0/impls/header.rs
• check that all types and implementations are organized clearly within their respective modules.

[jbearer]

Looks good, minus a few comments. I think @ggutoski should review types/src/v0/impls/block/ and types/src/v0/v0_1/block.rs, mainly just to sign off on the organization of things; I don't think any logic has changed.

Also, I think we need something like reference_tests and message_compat_tests for the new versions, so that if we make any breaking changes to any existing supported version, a test will fail

[ggutoski]

Looks good, minus a few comments. I think @ggutoski should review types/src/v0/impls/block/ and types/src/v0/v0_1/block.rs, mainly just to sign off on the organization of things; I don't think any logic has changed.

Every field in every struct is now pub(crate). This is a significant break of abstraction. I do not yet have a helpful suggestion on how to recover abstraction. Perhaps this break is a price worth paying. Happy to discuss further.

[jbearer]

Looks good, minus a few comments. I think @ggutoski should review types/src/v0/impls/block/ and types/src/v0/v0_1/block.rs, mainly just to sign off on the organization of things; I don't think any logic has changed.

Every field in every struct is now pub(crate). This is a significant break of abstraction. I do not yet have a helpful suggestion on how to recover abstraction. Perhaps this break is a price worth paying. Happy to discuss further.

Can we not just duplicate the old directory structure under types/src/v0/v0_1, bring back the pub(in ...), and use public methods to access these types for the trait impls?

[jbearer]

😮‍💨