(De-)Serialization of Transaction, PartialTransaction, Note

[bazzilic]

As we need to transfer such objects as transactions, partial transactions, notes, and some others over the network and between different systems, those need to be serialized and deserialized.

Preliminary, the decision is to use Borsh (https://borsh.io/) (de)serializer due to its performance, availability for multiple languages, consistent serialization (important if we need to hash or sign the transferred object), and a reliable dev team behind it.

It might make sense to define separate DTO structs and put them in a separate crate, so another codebase does not necessarily have to depend on Taiga as a whole to be able to work with these serialized objects.