MXS-1752: Add prototype concatenation router

The router concatenates multiple result sets.

server/modules/routing/cat/cat.hh

@@ -0,0 +1,39 @@
+#pragma once
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2020-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxscale/router.hh>
+
+class CatSession;
+
+/**
+ * The per instance data for the router.
+ */
+class Cat: public mxs::Router<Cat, CatSession>
+{
+    Cat(const Cat&) = delete;
+    Cat& operator =(const Cat&) = delete;
+public:
+    ~Cat();
+    static Cat* create(SERVICE* pService, char** pzOptions);
+    CatSession* newSession(MXS_SESSION* pSession);
+    void diagnostics(DCB* pDcb);
+    json_t* diagnostics_json() const;
+    uint64_t getCapabilities();
+
+private:
+    friend class CatSession;
+
+    /** Internal functions */
+    Cat(SERVICE* pService);
+};