docs: add authz reference info in the circuit antehandler (backport #20146) (#20155)

Co-authored-by: Reece Williams <31943163+Reecepbcups@users.noreply.github.com>

x/circuit/ante/circuit.go

@@ -24,6 +24,10 @@ func NewCircuitBreakerDecorator(ck CircuitBreaker) CircuitBreakerDecorator {
 	}
 }
 
+// If you copy this as reference and your app has the authz module enabled, you must either:
+// - recursively check for nested authz.Exec messages in this function.
+// - or error early if a nested authz grant is found.
+// The circuit AnteHandler handles this with baseapp's service router: https://github.com/cosmos/cosmos-sdk/issues/18632.
 func (cbd CircuitBreakerDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool, next sdk.AnteHandler) (sdk.Context, error) {
 	// loop through all the messages and check if the message type is allowed
 	for _, msg := range tx.GetMsgs() {