Add encode to ContractEncoder

[davidyuk]

This PR is supported by the Æternity Foundation

[davidyuk]

This is the most tricky part, I am not sure how to make it without breaking changes

[dincho]

I'd like to take a look into details:

• unicode strings implementation - why and how
• FateTypeAny - existant, implementation in the reference FATE

If you could split that in separate PR's it would be easier

[davidyuk]

FateTypeAny - existant, implementation in the reference FATE

Decoding the variant gives us a value, its type, and arities of other variants without knowing their types. I need arities to serialize the same variant value back. The idea is to use FateTypeAny as a placeholder since we don't know the actual types in this case. Do you have a better suggestion on what to use here?

[dincho]

Decoding the variant gives us a value, its type, and arities of other variants without knowing their types.

I'll check the docs and the referral implementation again, but IIRC that's correct.
I guess that's by design.

I need arities to serialize the same variant value back.

What's the real use-case of this?

[dincho]

@davidyuk could you rebase please

[davidyuk]

What's the real use-case of this?

In the case of contract encoding, I need this to encode the decoded contract without losing a variant type, to get the same bytecode.

It is generally needed to decode and then encode some fate raw value without ACI.