Go to Jira project configuration ** In Workflows tab Click EDIT Icon.
In Post Functions tab section, Click Add Post Function.
Choose HTTP Request API Invoke Function and Click Add.
Configure Post Function and Click Add.
Here is example to use Issue fields in JSON payload:
Note. You can find custom field ID at, Issues > Custom Fields > Click Edit > You will find in URL.
To generate basic access token with username and password:
Review and Click Publish.
Transition Issue and verify if HTTP Request triggered with response notification in issue comment.