Unschedule proposal when confirmations falls bellow `required` amount

[soloseng]

Description

Currently, when a proposal is scheduled and is waiting for the delay to be reached, any owner can revoke their confirmation during the delay period. However, revoking a confirmation only decrease the total number of confirmations for that proposal.

In the event that the total number of confirmations falls bellow the required threshold, a scheduled transaction can still be executed once the delay period has elapsed, rendering the timelock mechanism ineffective.

Proposed Fix

• add a new event UnscheduledProposal(uint256 proposalId)that is emitted when proposal is unscheduled.
• add a new function unscheduleProposal(uint256 proposalId) that is internal, only called by the revokeConfirmation() and resets timestampExecutable and emit ProposalUnscheduled(proposalId) event

The updated revokeConfirmation() logic would be as follows:

• After updating owner confirmation,
• check if proposal isScheduled() for execution.
  • if true => check if proposal isFullyConfirmed()
  • if false => unscheduleProposal(proposalId)

[soloseng]

After further discussion with the team, it was established that:

The main purpose of our timelock is to give users time to react and therefore the functionality to unschedule a proposals is not as important in our use case. Additionally, introducing unscheduleProposal could have unintended consequence of giving a single owner veto power over the proposals if only the minimum number of confirmations were initially submitted.

The decision was made to not change the current multiSig contract implementation.