@murugesan_munusamy this forum is a free offering solutions/discussion forum. You have to wait for until someone responds.
Hope you understand 
Meanwhile you can refer camunda documentation which will provide you a more insights.
In service task, you can write your own rest api using OkhttpClient or RestTemplate.
Creating same topic.
And moreover, don’t tag to posts to Announcements, unless if necessary. Because this tag is meant for newer version/community extension releases.
Have a nice day