Better flow rate allowance support for gnosis safe

[0xdavinchee]

Overview

Smart contract wallets will likely become more and more prevalent in the crypto ecosystem to improve wallet UX and general UX when using crypto.

There are currently some known pain points when setting up salaries or vesting via a gnosis safe and we aim to address this at the protocol level.

Current flow and rationale

From @vmichalik:

• when an admin is setting up salaries or vesting, they need to give flowrate allowance to open a stream
• if they are setting up multiple streams from a gnosis safe, they’ll go through the process to set up each scheduled stream, and those transactions will be pending on the multisig
• we have no way of knowing what the total flowrate allowance needs to be in the process of crafting each transaction by checking the current state since the other transactions are still pending
• if instead of updating the flow (without enough information), each transaction increases the flow, the total will always be correct
• this is way safer and better than unlimited approving flowrate

Solution for known issue

• Implement increaseFlowRateAllowance and decreaseFlowRateAllowance functions in ConstantFlowAgreementV1. This works the same as increaseAllowance and decreaseAllowance for SuperToken.
• Make increaseAllowance and decreaseAllowance a batch-able operation in Superfluid.sol.
• ??