Header structures

[asmie]

Description

This task is derived from #5 and only creates the header structures.

Header data structures are listed in Chapter 5 and then described in the next chapters.

Header:
H ≡ (Hp, Hr , Hx, Ht, He, Hw , Hj , Hk , Hv , Hs)

• Hp - parent header
• Hr - parent state root (root of Merkle tree)
• Hx - extrinsic hash is the hash of the block’s extrinsic data
• Ht - timeslot index
• He - epoch marker
• Hw - winning tickets marker
• Hj - the judgment marker
• Hk - a Bandersnatch block author key
• Hv - the entropy yielding VRF signature
• Hs - block seal
• Header serialization.

Serialization

The outputs of tasks #6 and #14 should be used to serialize header structures.

Deliverable

All of the header structures in Go code with tests (where appropriate).
All structures should be serializable.

Testing

There are no current official test vectors to check the results.

[asmie]

From the parent task:

Bandersnatch data types: Signature -> https://github.com/paritytech/polkadot-sdk/blob/master/substrate/primitives/core/src/bandersnatch.rs#L68

* needed for vrf signature and the block seal

Block Author Key -> https://github.com/paritytech/polkadot-sdk/blob/master/substrate/primitives/core/src/bandersnatch.rs#L79

* (Not sure if this is the correct key type yet)