workflow_job_template: empty value for webhook_credential is ignored instead of removing credential

[kk-at-redhat]

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• I agree to follow this project's code of conduct.
• I have checked the current issues for duplicates.
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• I am NOT reporting a (potential) security vulnerability. (These should be emailed to security@ansible.com instead.)

Bug Summary

When webhook_credential value is empty it is ignored instead of removing assigned credential which makes it impossible to remove credentials using automation.

AWX version

4.6.7

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• UI (tech preview)
• API
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• Other

Installation method

docker development environment

Modifications

no

Ansible version

2.15.13

Operating system

RHEL9

Web browser

No response

Steps to reproduce

ansible -m ansible.controller.workflow_job_template --args="name='Workflow B' webhook_credential='gh'" localhost

localhost | CHANGED => {
"changed": true,
"id": 99
}

ansible -m ansible.controller.workflow_job_template --args="name='Workflow B' webhook_credential=''" localhost

Expected results

localhost | CHANGED => {
"changed": true,
"id": 99
}

Actual results

localhost | SUCCESS => {
"changed": false,
"id": 99
}

Additional information

No response