[Feature]: New signer state machine for each input

[djordon]

Feature - New signer state machine for each input

1. Description

Whenever a signer gets a sign request over a particular message, the signers create a state machine if its for a transaction ID that they have never seen before. But this ties the signing shares to transaction when it should be tied to the input that is being signed since a transaction can contained inputs locked by different keys.

1.1 Context & Purpose

We need to support running deposits locked with different aggregate keys.

2. Technical Details:

When a signer receives a NonceRequest message they should create a new state machine associated with the message that they being are asked to sign. Then, when the signer receives a subsequent SignatureShareRequest message, they provide their signature shares if a state machine exists for the message to be signed and exit otherwise. At the end of they should delete the state machine from memory. This is similar to the current flow, but oriented around messages instead of txids.

2.1 Acceptance Criteria:

• The signers create new state machines for each message that they sign

3. Related Issues and Pull Requests (optional):