feat(cat-voices): encode/decode cose documents

[dtscalac]

Description

Adds utils around encoding/decoding/signing COSE_SIGN documents for proposals. The Document is not limited to a proposal, it can handle anything that can be represented as a binary list: json, images or any other format that can be encoded/decoded as bytes.

Limitations:

• The DocumentManager assumes ED25519 signature algorithm and won't work with different ones unless we decide we want to support others.
• The DocumentManager always compresses the document using brotli compression but it can receive both compressed or uncompressed document depending on the "content encoding" header from COSE_SIGN.
• Not supporting yet document versions or template references, do we need it now?

Related Issue(s)

Closes #1400

Description of Changes

How to use the util:

1. Define a document

final class _JsonDocument extends Equatable implements BinaryDocument {
  final String title;

  const _JsonDocument(this.title);

  factory _JsonDocument.fromBytes(Uint8List bytes) {
    final string = utf8.decode(bytes);
    final map = json.decode(string);
    return _JsonDocument.fromJson(map as Map<String, dynamic>);
  }

  factory _JsonDocument.fromJson(Map<String, dynamic> map) {
    return _JsonDocument(map['title'] as String);
  }

  Map<String, dynamic> toJson() {
    return {'title': title};
  }

  @override
  Uint8List toBytes() {
    final jsonString = json.encode(toJson());
    return utf8.encode(jsonString);
  }

  @override
  DocumentContentType get contentType => DocumentContentType.json;

  @override
  List<Object?> get props => [title];
}

2. Sign it, encode/decode and verify it:

    test(
        'signDocument creates a signed document '
        'that can be converted from/to bytes', () async {
      const document = _JsonDocument('title');

      final signedDocument = await documentManager.signDocument(
        document,
        publicKey: _publicKey,
        privateKey: _privateKey,
      );

      expect(signedDocument.document, equals(document));

      final isVerified = await signedDocument.verifySignature(_publicKey);
      expect(isVerified, isTrue);

      final signedDocumentBytes = signedDocument.toBytes();
      final parsedDocument = await documentManager.parseDocument(
        signedDocumentBytes,
        parser: _JsonDocument.fromBytes,
      );

      expect(parsedDocument, equals(signedDocument));
    });

Please confirm the following checks

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream module

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[github-actions]

❌ Test Report | ${\color{lightgreen}Pass: 366/367}$ | ${\color{red}Fail: 1/367}$ |

[github-actions]

❌ Test Report | ${\color{lightgreen}Pass: 366/367}$ | ${\color{red}Fail: 1/367}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[stevenj]

@dtscalac I added @saibatizoku to also do a review because hes doing the backend side of this.
Just to double check alignment

[stevenj]

@dtscalac further to the comment above about getting @saibatizoku to do a review. He has a PR in catalyst-libs for a decoder library. see: input-output-hk/catalyst-libs#101

Work with @saibatizoku by generating some signed docs using your code here so he can validate them against his decoder.
Ideally that should work, but if not we need to find out what side isn't working properly before merging. Easier to test it now together as both sides of the process are ready of review together.

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 367/367}$ | ${\color{red}Fail: 0/367}$ |

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 370/370}$ | ${\color{red}Fail: 0/370}$ |

[saibatizoku]

Looks good to me.