I'm trying to automate the api endpoints added under "Configure System". I believe the plugin is https://wiki.jenkins.io/display/JENKINS/GitHub+Branch+Source+Plugin. (v.2.4.2). The property is simply left out. 

I'm also experiencing this https://issues.jenkins-ci.org/browse/JENKINS-54051 when trying to add the api, although when using the setting it works as expected. 

Jenkins is set up with https://github.com/helm/charts/tree/master/stable/jenkins, haven't really tweaked anything particular, but these are the plugins I provide:

InstallPlugins:

• kubernetes:1.14.3
• workflow-aggregator:2.5
• workflow-job:2.31
• credentials-binding:1.17
• git:3.9.3
• github-branch-source:2.4.2
• pipeline-utility-steps:2.2.0
• role-strategy:2.9.0
• http_request:1.8.22

Also, running Jenkins ver. 2.164.