[Feature]: Signers store bitcoin sighashes and decisions

[djordon]

Feature - Signers store bitcoin sighashes and decisions

1. Description

This is ticket corresponds to point (5) in 3.1 in #782. Signers stores sighash digests, along with whether they will sign for them, in their databases.

1.1 Context & Purpose

Each signer records their decision for easy look-up before participating in a signing round.

2. Technical Details:

We need a new table that stores the sighashes and the signers decisions.

2.1 Acceptance Criteria:

• Signers store enough information in the database to know whether they will participate in a signing round for a sighash.

3. Related Issues and Pull Requests (optional):

Relates to:

• [Feature]: Signers check sighash before participating in signing rounds #793
• [Feature]: Validate bitcoin transaction sign requests #286
• [Design]: Signing bitcoin transactions #782