0.23rc4

Originally released on 2019-11-15 11:42:02+00:00 (link).

Internal changes:

• Avoid logging of empty meaningless diffs in on-resume handlers. #236
• Avoid patching the objects if there is no need to patch (and skip logging). #236
• Avoid purging the handler progress if there is only one handler (and skip logging). #236
• Add kex as an alias for KopfExample CRD for demos/docs. #235