multi: fix all linter errors

auth/authenticator_test.go

@@ -8,16 +8,9 @@ import (
 
 	"github.com/lightninglabs/kirin/auth"
 	"github.com/lightninglabs/loop/lsat"
-	"github.com/lightningnetwork/lnd/lntypes"
 	"gopkg.in/macaroon.v2"
 )
 
-type mockChallenger struct{}
-
-func (c *mockChallenger) NewChallenge() (string, lntypes.Hash, error) {
-	return "lnt1xxxx", lntypes.ZeroHash, nil
-}
-
 // createDummyMacHex creates a valid macaroon with dummy content for our tests.
 func createDummyMacHex(preimage string) string {
 	dummyMac, err := macaroon.New(