multi: add blinded paths to invoices

Expose the ability to add blinded paths to an invoice. Also expose
various configuration values.

We also let the lncfg.Invoices struct satisfy the Validator interface so
that we can verify all its config values in one place.

config.go

@@ -680,6 +680,13 @@ func DefaultConfig() Config {
 		},
 		Invoices: &lncfg.Invoices{
 			HoldExpiryDelta: lncfg.DefaultHoldInvoiceExpiryDelta,
+			BlindedPaths: lncfg.BlindedPaths{
+				MinNumRealHops:           lncfg.DefaultMinNumRealBlindedPathHops,
+				NumHops:                  lncfg.DefaultNumBlindedPathHops,
+				MaxNumPaths:              lncfg.DefaultMaxNumBlindedPaths,
+				PolicyIncreaseMultiplier: lncfg.DefaultBlindedPathPolicyIncreaseMultiplier,
+				PolicyDecreaseMultiplier: lncfg.DefaultBlindedPathPolicyDecreaseMultiplier,
+			},
 		},
 		MaxOutgoingCltvExpiry:     htlcswitch.DefaultMaxOutgoingCltvExpiry,
 		MaxChannelFeeAllocation:   htlcswitch.DefaultMaxLinkFeeAllocation,
@@ -1656,18 +1663,6 @@ func ValidateConfig(cfg Config, interceptor signal.Interceptor, fileParser,
 		return nil, mkErr("error parsing gossip syncer: %v", err)
 	}
 
-	// Log a warning if our expiry delta is not greater than our incoming
-	// broadcast delta. We do not fail here because this value may be set
-	// to zero to intentionally keep lnd's behavior unchanged from when we
-	// didn't auto-cancel these invoices.
-	if cfg.Invoices.HoldExpiryDelta <= lncfg.DefaultIncomingBroadcastDelta {
-		ltndLog.Warnf("Invoice hold expiry delta: %v <= incoming "+
-			"delta: %v, accepted hold invoices will force close "+
-			"channels if they are not canceled manually",
-			cfg.Invoices.HoldExpiryDelta,
-			lncfg.DefaultIncomingBroadcastDelta)
-	}
-
 	// If the experimental protocol options specify any protocol messages
 	// that we want to handle as custom messages, set them now.
 	customMsg := cfg.ProtocolOptions.CustomMessageOverrides()
@@ -1690,6 +1685,7 @@ func ValidateConfig(cfg Config, interceptor signal.Interceptor, fileParser,
 		cfg.RemoteSigner,
 		cfg.Sweeper,
 		cfg.Htlcswitch,
+		cfg.Invoices,
 	)
 	if err != nil {
 		return nil, err