ChangeOperation has various static methods to construct:
https://files.inductiveautomation.com/sdk/javadoc/ignition81/8.1.21/com/inductiveautomation/ignition/common/project/ChangeOperation.html#newCreateOp(com.inductiveautomation.ignition.common.project.resource.ProjectResource)
A ProjectManager can be retrieved from GatewayContext.