config: expose gossip.pinned-syncers for conf

The pinned syncer set is exposed as a comma-separated list of pubkeys.

lncfg/gossip.go

@@ -0,0 +1,28 @@
+package lncfg
+
+import (
+	"github.com/lightningnetwork/lnd/discovery"
+	"github.com/lightningnetwork/lnd/routing/route"
+)
+
+type Gossip struct {
+	PinnedSyncersRaw []string `long:"pinned-syncers" description:"A set of peers that should always remain in an active sync state, which can be used to closely synchronize the routing tables of two nodes. The value should be comma separated list of hex-encoded pubkeys. Connected peers matching this pubkey will remain active for the duration of the connection and not count towards the NumActiveSyncer count."`
+
+	PinnedSyncers discovery.PinnedSyncers
+}
+
+// Parse the pubkeys for the pinned syncers.
+func (g *Gossip) Parse() error {
+	pinnedSyncers := make(discovery.PinnedSyncers)
+	for _, pubkeyStr := range g.PinnedSyncersRaw {
+		vertex, err := route.NewVertexFromStr(pubkeyStr)
+		if err != nil {
+			return err
+		}
+		pinnedSyncers[vertex] = struct{}{}
+	}
+
+	g.PinnedSyncers = pinnedSyncers
+
+	return nil
+}