Implements both v0 (BIP-174) and v2 (BIP-370) versions of PSBT specification.
Minimal-dependency, no-std, 100% standard compliant, with no non-standard assumptions.
Differs PSBT from bitcoin crate in the following ways:
- supports PSBT v2;
- preserves the original content of PSBT (i.e. serialization of PSBT with no modifications always strictly match the original serialization);
- simplifies workflow for managing custom keys.