Delegate

A delegate contract is a way of providing extensions to a treasury that augments the default JBPayoutRedemptionPaymentTerminal3_1_1 behavior.
Pay delegates include a custom didPay(...) hook that will execute after all of the default protocol pay logic has successfully executed in the terminal contract. The hook is passed a bunch of contextual information via a JBDidPayData data structure.
Redemption delegates include a custom didRedeem(...) hook that will execute after all of the default protocol redeem logic has successfully executed in the terminal contract. The hook is passed a bunch of contextual information via a JBDidRedeemData data structure. The didRedeem(...) hook gets called before any reclaimed tokens are transferred out of the terminal contract.
Each IJBPaymentTerminal fork can leverage delegates in unique ways.

There are two types of delegates: IJBPayDelegate3_1_1s and IJBRedemptionDelegate3_1_1s. Any contract that adheres to these interfaces can be used as a delegate in a project's funding cycles.
The funding cycle's dataSource specifies the active Delegate contracts.
The IJBPayDelegate3_1_1's didPay(...) hook is triggered in JBPayoutRedemptionPaymentTerminal3_1_1._pay(...), and the IJBRedemptionDelegate's didRedeem(...) hook is triggered in JBPayoutRedemptionPaymentTerminal3_1_1.redeemTokensOf(...).
The redemption delegate hook is called before funds are dispersed.