Expose Register Multisignature schema and message tag constants

[ishantiw]

Description

To support off-chain services to support multisignature registration we need to expose schema that will be used to be signed by members of MS registration transaction. Also to use message tag constants, we need to expose it from the SDK.

We can either expose these constants through RPC or simple export from the SDK, yet to be decided.

Additional Information

• Multisignature Registration message Schema: https://github.com/LiskHQ/lisk-sdk/blob/dd2a20124a6c4a128b227f0d0c3915fc9d9937d0/framework/src/modules/auth/schemas.ts#L107

[ishantiw]

Resolved in https://github.com/LiskHQ/lisk-sdk/pull/7733