Webhook for Jenkins HTTP API doesn't work when separating Token from URL
Summary
Webhook for Jenkins doesn't work when separating Token from URL
Steps to reproduce
Under Integration -> Webhooks. When I add a webhook for a tag push event (for example) to trigger a Jenkins build, I can do this by using the form:
URL: https://<username>:<token>@<my-jenkins-url>/blah/jenkins/job/blah/build
Secret Token: <blank field>
This works. So I know that the communication path is sound. However, it leaves the ugly username and token fields exposed in the list of webhooks for all and sundry to see:
When I try and split the URL from the Token, the resultant URL+token combo doesn't work:
I tried this form:
URL: https://<username>@<my-jenkins-url>/blah/jenkins/job/blah/build
Secret Token: <token>
This results in an '500 error' page when I click on Test

When I try this form:
URL: https://<my-jenkins-url>/blah/jenkins/job/blah/build
Secret Token: <user>:<token>
I get a red banner 404 error like this:

When I try this form (remove username):
URL: https://<my-jenkins-url>/blah/jenkins/job/blah/build
Secret Token: <token>
I get the same red banner 404 error as above:
What is the current bug behavior?
Fails as described above
What is the expected correct behavior?
The Broken up form of URL and Token should work the same way the combined form does.
Results of GitLab environment info
Using GitLab Community Edition 8.17.3 f0c970ec
Using Jenkins version 1.565.1