multi: add ChannelGraph Config struct

And use this struct to pass NewChannelGraph anything it needs to be able
to init the KVStore that it houses. This will allow us to add
ChannelGraph specific options.

graph/db/graph.go

@@ -2,6 +2,18 @@ package graphdb
 
 import "github.com/lightningnetwork/lnd/kvdb"
 
+// Config is a struct that holds all the necessary dependencies for a
+// ChannelGraph.
+type Config struct {
+	// KVDB is the kvdb.Backend that will be used for initializing the
+	// KVStore CRUD layer.
+	KVDB kvdb.Backend
+
+	// KVStoreOpts is a list of functional options that will be used when
+	// initializing the KVStore.
+	KVStoreOpts []KVStoreOptionModifier
+}
+
 // ChannelGraph is a layer above the graph's CRUD layer.
 //
 // NOTE: currently, this is purely a pass-through layer directly to the backing
@@ -12,10 +24,8 @@ type ChannelGraph struct {
 }
 
 // NewChannelGraph creates a new ChannelGraph instance with the given backend.
-func NewChannelGraph(db kvdb.Backend, options ...KVStoreOptionModifier) (
-	*ChannelGraph, error) {
-
-	store, err := NewKVStore(db, options...)
+func NewChannelGraph(cfg *Config) (*ChannelGraph, error) {
+	store, err := NewKVStore(cfg.KVDB, cfg.KVStoreOpts...)
 	if err != nil {
 		return nil, err
 	}