Add initial producer code

include/cppkafka/kafka_handle_base.h

@@ -0,0 +1,33 @@
+#ifndef CPPKAFKA_KAFKA_HANDLE_BASE_H
+#define CPPKAFKA_KAFKA_HANDLE_BASE_H
+
+#include <string>
+#include <memory>
+#include <librdkafka/rdkafka.h>
+
+namespace cppkafka {
+
+class Topic;
+class TopicConfiguration;
+
+class KafkaHandleBase {
+public:
+    virtual ~KafkaHandleBase() = default;
+
+    rd_kafka_t* get_handle();
+    Topic get_topic(const std::string& name);
+    Topic get_topic(const std::string& name, const TopicConfiguration& config);
+protected:
+    KafkaHandleBase();
+    KafkaHandleBase(rd_kafka_t* handle);
+
+    void set_handle(rd_kafka_t* handle);
+private:
+    using HandlePtr = std::unique_ptr<rd_kafka_t, decltype(&rd_kafka_destroy)>;
+
+    HandlePtr handle_;
+};
+
+} // cppkafka
+
+#endif // CPPKAFKA_KAFKA_HANDLE_BASE_H