Revert "staticaddr: remove an unused interface method"

This reverts commit cc5113d.

Author: hieblmi

staticaddr/withdraw/interface.go

@@ -8,6 +8,7 @@ import (
 	"github.com/lightninglabs/loop/staticaddr/address"
 	"github.com/lightninglabs/loop/staticaddr/deposit"
 	"github.com/lightninglabs/loop/staticaddr/script"
+	"github.com/lightningnetwork/lnd/lnwallet"
 )
 
 // Store is the database interface that is used to store and retrieve
@@ -31,6 +32,10 @@ type AddressManager interface {
 	// GetStaticAddress returns the deposit address for the given
 	// client and server public keys.
 	GetStaticAddress(ctx context.Context) (*script.StaticAddress, error)
+
+	// ListUnspent returns a list of utxos at the static address.
+	ListUnspent(ctx context.Context, minConfs,
+		maxConfs int32) ([]*lnwallet.Utxo, error)
 }
 
 type DepositManager interface {