Add modified Replicator for avrorouter

Repurposed the Replicator from the CDC integration project as a
replication event processing service. It is similar to the CDC version of
the Replicator and is still in the same namespace but it lacks all of the
cross-thread communication that was a part of the integration project.

server/modules/routing/avrorouter/replicator.hh

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2019 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: 2022-01-01
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include <string>
+#include <memory>
+
+#include "config.hh"
+#include "rpl.hh"
+
+namespace cdc
+{
+
+// Final name pending
+class Replicator
+{
+public:
+    Replicator(const Replicator&) = delete;
+    Replicator& operator=(const Replicator&) = delete;
+
+    /**
+     * Create a new data replicator
+     *
+     * @param cnf The configuration to use
+     *
+     * @return The new Replicator instance
+     */
+    static std::unique_ptr<Replicator> start(const Config& cnf, Rpl* rpl);
+
+    /**
+     * Check if the replicator is OK
+     *
+     * @return True if everything is OK. False if any errors have occurred and the replicator has stopped.
+     */
+    bool ok() const;
+
+    /**
+     * Destroys the Replicator and stops the processing of data
+     */
+    ~Replicator();
+
+private:
+    class Imp;
+    Replicator(const Config& cnf, Rpl* rpl);
+
+    // Pointer to the implementation of the abstract interface
+    std::unique_ptr<Replicator::Imp> m_imp;
+};
+}