rpcserver: AddInvoice uses groupkey

In this commit we take the user defined group key and allow the asset
specifier to be created over it. All the calls that accept it as an
argument are already groupkey aware.

Author: GeorgeTsagk

rpcserver.go

@@ -7684,18 +7684,31 @@ func checkOverpayment(quote *rfqrpc.PeerAcceptedSellQuote,
 func (r *rpcServer) AddInvoice(ctx context.Context,
 	req *tchrpc.AddInvoiceRequest) (*tchrpc.AddInvoiceResponse, error) {
 
+	if len(req.AssetId) > 0 && len(req.GroupKey) > 0 {
+		return nil, fmt.Errorf("cannot set both asset id and group key")
+	}
+
 	if req.InvoiceRequest == nil {
 		return nil, fmt.Errorf("invoice request must be specified")
 	}
 	iReq := req.InvoiceRequest
 
-	// Do some preliminary checks on the asset ID and make sure we have any
-	// balance for that asset.
-	if len(req.AssetId) != sha256.Size {
-		return nil, fmt.Errorf("asset ID must be 32 bytes")
+	var specifier asset.Specifier
+
+	assetID, groupKey, err := parseAssetSpecifier(
+		req.AssetId, "", req.GroupKey, "",
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	switch {
+	case assetID != nil:
+		specifier = asset.NewSpecifierFromId(*assetID)
+
+	case groupKey != nil:
+		specifier = asset.NewSpecifierFromGroupKey(*groupKey)
 	}
-	var assetID asset.ID
-	copy(assetID[:], req.AssetId)
 
 	// The peer public key is optional if there is only a single asset
 	// channel.
@@ -7710,8 +7723,6 @@ func (r *rpcServer) AddInvoice(ctx context.Context,
 		peerPubKey = &parsedKey
 	}
 
-	specifier := asset.NewSpecifierFromId(assetID)
-
 	// We can now query the asset channels we have.
 	assetChan, err := r.rfqChannel(
 		ctx, specifier, peerPubKey, ReceiveIntention,
@@ -7733,15 +7744,13 @@ func (r *rpcServer) AddInvoice(ctx context.Context,
 		time.Duration(expirySeconds) * time.Second,
 	)
 
+	rpcSpecifier := marshalAssetSpecifier(specifier)
+
 	resp, err := r.AddAssetBuyOrder(ctx, &rfqrpc.AddAssetBuyOrderRequest{
-		AssetSpecifier: &rfqrpc.AssetSpecifier{
-			Id: &rfqrpc.AssetSpecifier_AssetId{
-				AssetId: assetID[:],
-			},
-		},
-		AssetMaxAmt: req.AssetAmount,
-		Expiry:      uint64(expiryTimestamp.Unix()),
-		PeerPubKey:  peerPubKey[:],
+		AssetSpecifier: &rpcSpecifier,
+		AssetMaxAmt:    req.AssetAmount,
+		Expiry:         uint64(expiryTimestamp.Unix()),
+		PeerPubKey:     peerPubKey[:],
 		TimeoutSeconds: uint32(
 			rfq.DefaultTimeout.Seconds(),
 		),