wtclient+lnrpc: move RemoveTower to Manager

Simiarly to the previous commit, this commit moves the RemoveTower
method from the Client to the TowerClientManager interface. The manager
handles any DB related handling. The manager will first attempt to
remove the tower from the in-memory state of each client and then will
attempt to remove the tower from the DB. If the removal from the DB
fails, the manager will re-add the tower to the in-memory state of each
client.

watchtower/wtclient/manager.go

@@ -2,9 +2,11 @@ package wtclient
 
 import (
 	"fmt"
+	"net"
 	"sync"
 	"time"
 
+	"github.com/btcsuite/btcd/btcec/v2"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/channeldb"
@@ -24,6 +26,13 @@ type TowerClientManager interface {
 	// any new addresses included will be considered when dialing it for
 	// session negotiations and backups.
 	AddTower(*lnwire.NetAddress) error
+
+	// RemoveTower removes a watchtower from being considered for future
+	// session negotiations and from being used for any subsequent backups
+	// until it's added again. If an address is provided, then this call
+	// only serves as a way of removing the address from the watchtower
+	// instead.
+	RemoveTower(*btcec.PublicKey, net.Addr) error
 }
 
 // Config provides the TowerClient with access to the resources it requires to
@@ -243,3 +252,50 @@ func (m *Manager) AddTower(address *lnwire.NetAddress) error {
 
 	return nil
 }
+
+// RemoveTower removes a watchtower from being considered for future session
+// negotiations and from being used for any subsequent backups until it's added
+// again. If an address is provided, then this call only serves as a way of
+// removing the address from the watchtower instead.
+func (m *Manager) RemoveTower(key *btcec.PublicKey, addr net.Addr) error {
+	// We'll load the tower before potentially removing it in order to
+	// retrieve its ID within the database.
+	dbTower, err := m.cfg.DB.LoadTower(key)
+	if err != nil {
+		return err
+	}
+
+	m.clientsMu.Lock()
+	defer m.clientsMu.Unlock()
+
+	for _, client := range m.clients {
+		err := client.removeTower(dbTower.ID, key, addr)
+		if err != nil {
+			return err
+		}
+	}
+
+	if err := m.cfg.DB.RemoveTower(key, addr); err != nil {
+		// If the persisted state update fails, re-add the address to
+		// our client's in-memory state.
+		tower, newTowerErr := NewTowerFromDBTower(dbTower)
+		if newTowerErr != nil {
+			log.Errorf("could not create new in-memory tower: %v",
+				newTowerErr)
+
+			return err
+		}
+
+		for _, client := range m.clients {
+			addTowerErr := client.addTower(tower)
+			if addTowerErr != nil {
+				log.Errorf("could not re-add tower: %v",
+					addTowerErr)
+			}
+		}
+
+		return err
+	}
+
+	return nil
+}