fix: Spring Boot 4.0 breaking changes — migrate to Jackson 3 Kafka serializers

[Copilot]

Spring Boot 4.0 drops Jackson 2 (com.fasterxml.jackson) in favor of Jackson 3 (tools.jackson), breaking compilation due to missing TypeReference and ObjectMapper classes. Spring Kafka 4.0 deprecates JsonDeserializer/JsonSerializer in favor of Jackson 3-native replacements.

Changes

• KafkaConfiguration.java

  • Replace JsonDeserializer / JsonSerializer (Spring Kafka, Jackson 2-based) with JacksonJsonDeserializer
  • Fix pre-existing bug: JsonSerializer.class was incorrectly set as VALUE_DESERIALIZER_CLASS_CONFIG

• ProductsPactTest.java

  • Update ObjectMapper import: com.fasterxml.jackson.databind → tools.jackson.databind

// Before
import org.springframework.kafka.support.serializer.JsonDeserializer;
import org.springframework.kafka.support.serializer.JsonSerializer;
props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, JsonSerializer.class); // bug: wrong class
return new DefaultKafkaConsumerFactory<>(props, new StringDeserializer(), new JsonDeserializer<>(Product.class));

// After
import org.springframework.kafka.support.serializer.JacksonJsonDeserializer;
props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, JacksonJsonDeserializer.class);
return new DefaultKafkaConsumerFactory<>(props, new StringDeserializer(), new JacksonJsonDeserializer<>(Product.class));

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[Copilot]

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