wathtower/blob+wtserver: support anchor sessions

watchtower/wtserver/server.go

@@ -96,7 +96,10 @@ type Server struct {
 // sessions and send state updates.
 func New(cfg *Config) (*Server, error) {
 	localInit := wtwire.NewInitMessage(
-		lnwire.NewRawFeatureVector(wtwire.AltruistSessionsOptional),
+		lnwire.NewRawFeatureVector(
+			wtwire.AltruistSessionsOptional,
+			wtwire.AnchorCommitOptional,
+		),
 		cfg.ChainHash,
 	)
 

watchtower/wtserver/server_test.go

@@ -161,6 +161,28 @@ type createSessionTestCase struct {
 }
 
 var createSessionTests = []createSessionTestCase{
+	{
+		name: "duplicate session create altruist anchor commit",
+		initMsg: wtwire.NewInitMessage(
+			lnwire.NewRawFeatureVector(),
+			testnetChainHash,
+		),
+		createMsg: &wtwire.CreateSession{
+			BlobType:     blob.TypeAltruistAnchorCommit,
+			MaxUpdates:   1000,
+			RewardBase:   0,
+			RewardRate:   0,
+			SweepFeeRate: 10000,
+		},
+		expReply: &wtwire.CreateSessionReply{
+			Code: wtwire.CodeOK,
+			Data: []byte{},
+		},
+		expDupReply: &wtwire.CreateSessionReply{
+			Code: wtwire.CodeOK,
+			Data: []byte{},
+		},
+	},
 	{
 		name: "duplicate session create",
 		initMsg: wtwire.NewInitMessage(