Username: {your email address associated with the Jira account you have generated the API token from}
Password: {your Jira API token}
Body:
{ "transition": { "id": "41" } }
Note: ‘ID’ above needs to be the actual ID associated with the ‘Done’ Status (or whatever you have) from your Jira project. You can view what the ID numbers are by going to your Project Settings > Workflows and then selecting to the Edit icon on the far right of the workflow:
In the Edit mode, you will now see the ID numbers next to each Status stage: