[#86] Add alphabet contract processor

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/innerring/invoke/alphabet.go

@@ -0,0 +1,20 @@
+package invoke
+
+import (
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neofs-node/pkg/morph/client"
+)
+
+const (
+	emitMethod = "emit"
+)
+
+// AlphabetEmit invokes emit method on alphabet contract.
+func AlphabetEmit(cli *client.Client, con util.Uint160) error {
+	if cli == nil {
+		return client.ErrNilClient
+	}
+
+	// there is no signature collecting, so we don't need extra fee
+	return cli.Invoke(con, 0, emitMethod)
+}