wtclient: add anchor-aware session negotiation and filtering

watchtower/wtclient/session_negotiator.go

@@ -112,8 +112,19 @@ var _ SessionNegotiator = (*sessionNegotiator)(nil)
 
 // newSessionNegotiator initializes a fresh sessionNegotiator instance.
 func newSessionNegotiator(cfg *NegotiatorConfig) *sessionNegotiator {
+	// Generate the set of features the negitator will present to the tower
+	// upon connection. For anchor channels, we'll conditionally signal that
+	// we require support for anchor channels depdening on the requested
+	// policy.
+	features := []lnwire.FeatureBit{
+		wtwire.AltruistSessionsRequired,
+	}
+	if cfg.Policy.IsAnchorChannel() {
+		features = append(features, wtwire.AnchorCommitRequired)
+	}
+
 	localInit := wtwire.NewInitMessage(
-		lnwire.NewRawFeatureVector(wtwire.AltruistSessionsRequired),
+		lnwire.NewRawFeatureVector(features...),
 		cfg.ChainHash,
 	)