chore: extract listener method

[oguzyildirim]

We can extract the listener [^1] method and divide it into two. One method may create couchbase events ¹ and one method uses a mapper and produce events ².

[^1] : https://github.com/Trendyol/go-kafka-connect-couchbase/blob/master/connector.go#L42

Footnotes

1. https://github.com/Trendyol/go-kafka-connect-couchbase/blob/master/connector.go#L43 ↩

2. https://github.com/Trendyol/go-kafka-connect-couchbase/blob/master/connector.go#L55 ↩