ExtrinsicV5 Signature support

[TarikGul]

ExtrinsicV5 needs signing support through TransactionExtensions. This means that the api needs to support VerifySignature. This will be a bit awkward for the api since signing use to be done directly on the api, but now it will be done through a TransactionExtension.

Some type of workflow will need to be established here, as well as correcting the docs on signing in the future for V5.

[valentinfernandez1]

I’ve been working on the implementation for a while on the feat/v5-refactorbranch. The goal is to refactor the current V5 implementation, which has several issues when adding signature support.

The main problem with the current design is that Bare (ExtrinsicV5.ts) and General (GeneralExtrinsicV5.ts) extrinsics are implemented as separate classes. An extrinsic is initially created as a Bare extrinsic, but in order to be signed, it must be upgraded to a General extrinsic. This transition isn’t possible because it would require the instance type to change from GenericExtrinsicV5 to GeneralExtrinsicV5.

To resolve this, I’m refactoring the code so that all the necessary behavior is contained within a single class, similar to how it worked in ExtrinsicV4, where unsigned and signed extrinsics were represented by the same class.

This new ExtrinsicV5 class is initially constructed only with the method and the bare preamble but the internal state can later be upgraded to general if necessary.

Also spent some time adding definitions for transactionExtensions as they where missing from the registry and made it so it would use transactionsExtensions over signedExtensions when metadata 16 is available.

Currently I find myself stuck while testing the payload construction. Basically the payload is constructed here

export class ExtrinsicPayloadV5 extends Struct {
  constructor(registry: Registry, value?: ExtrinsicPayloadValue | Uint8Array | HexString, includeSignature: boolean = false) {
    const exTypes = registry.getTransactionExtensionTypes();
    const exExtra = registry.getTransactionExtensionExtra();

    super(registry, objectSpread(
      { method: 'Bytes' },
      exTypes,
      exExtra
    ), value);
  }

If the VerifySignature transactionExtension is part of the types it will fail to construct with the error

Error: Struct: failed on signature: Type:: DoNotConstruct: Cannot construct unknown type PalletVerifySignatureExtensionVerifySignature

Where PalletVerifySignatureExtensionVerifySignature:

  interface PalletVerifySignatureExtensionVerifySignature extends Enum {
    readonly isSigned: boolean;
    readonly asSigned: {
      readonly signature: SpRuntimeMultiSignature;
      readonly account: AccountId32;
    } & Struct;
    readonly isDisabled: boolean;
    readonly type: 'Signed' | 'Disabled';
  }

I have tried many approaches to making this type work but I find myself stuck right now. Feedback on how to approach it would be greatly appreciated.