Kibana Webhook to Ansible Tower Doesn't work

I am trying to run an Ansible tower with Kibana webhook connector but it's not working. This playbook works fine by using "curl -X POST -u username:password https://mytower.company.com/api/v2/job_templates/99/launch/ and does not require any other parameters in the body. However, when I configure the POST in Kibana connector, with Authentication turned on, and only use {} in the body and run the test, it always fail with this error:
Test failed to run

The following error was found:
error calling webhook, invalid response
Details:
[415] Unsupported Media Type

Looking at Ansible log, it looks like Kibana is not passing the username and password to Ansible:
awx.api.generics status 415 received by user AnonymousUser attempting to access /api/v2/job_templates/99/launch/

Does anyone know how to pass the basic credentials to Ansible tower in the webhook? Is there a way to add the credential in the body in "Create an action" section of the connector? Thanks in advance.