In 1.15.1 JENKINS-56082 introduced the ability to merge yaml fragments when merging pod templates.

Notably, it changed the persisted form of yaml from a String to a List<String> (source)

In some use cases we have at CloudBees, this is breaking persistence capability as KubernetesCloud objects are being copied between different Jenkins instances. Adding a field is usually fine except here it is replacing an existing field.

As the List<String> is only used for use cases of merging pod templates (a single textfield was exposed in the UI), where these are actually transient and never persisted, I am going to revert persistence to a single String field in order to achieve compatibility.