Add CPPKAFKA_API to utils classes

include/cppkafka/utils/backoff_performer.h

@@ -40,7 +40,7 @@ namespace cppkafka {
 /**
  * 
  */
-class BackoffPerformer {
+class CPPKAFKA_API BackoffPerformer {
 public:
     using TimeUnit = std::chrono::milliseconds;
     static constexpr TimeUnit DEFAULT_INITIAL_BACKOFF{100};

include/cppkafka/utils/buffered_producer.h

@@ -59,7 +59,7 @@ namespace cppkafka {
  * This class is not thread safe.
  */
 template <typename BufferType>
-class BufferedProducer {
+class CPPKAFKA_API BufferedProducer {
 public:
     /**
      * Concrete builder

include/cppkafka/utils/compacted_topic_processor.h

@@ -43,7 +43,7 @@ namespace cppkafka {
  * \brief Events generated by a CompactedTopicProcessor
  */
 template <typename Key, typename Value>
-class CompactedTopicEvent {
+class CPPKAFKA_API CompactedTopicEvent {
 public:
     /**
      * \brief Event type enum

include/cppkafka/utils/consumer_dispatcher.h

@@ -70,7 +70,7 @@ namespace cppkafka {
  * * EOF: void(BasicConsumerDispatcher::EndOfFile, TopicPartition)
  */
 template <typename ConsumerType>
-class BasicConsumerDispatcher {
+class CPPKAFKA_API BasicConsumerDispatcher {
 public:
     /**
      * Tag to indicate a timeout occurred