Kafka HTTP Source connector - SunCertPathBuilderException: unable to find valid certification path to requested target

I am trying to use https://github.com/llofberg/kafka-connect-rest connector to retrieve data from api.

I successfully built source code and installed plugin into Kafka Connect. But I cannot connect to api using https and get following error.

Caused by: javax.net.ssl.SSLHandshakeException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

Connector configuration is following

"name": "RestSourceConnectorSpring","config": {"producer.compression.type": "snappy","connector.class": "com.tm.kafka.connect.rest.RestSourceConnector","tasks.max": "1","rest.source.poll.interval.ms": "10000","rest.source.method": "GET","rest.source.url": "https://myapi.testapi.com/subjects","rest.source.headers": "Content-Type:application/json,Accept:application/json","rest.source.topic.selector": "com.tm.kafka.connect.rest.selector.SimpleTopicSelector","rest.source.destination.topics": "restSourceDestinationTopic"  }}

myapi.testapi.com has let's encrypt certificate and I can get required json data from browser.

How can I provide SSL configuration to retrieve data?