Headless Server Library Update of Snake YAML

Snake YAML library was updated from org.yaml:snakeyaml:1.29 to org.yaml:snakeyaml:1.31

(CMS-22082)

Expose id of CMPlaceholder

Expose the CMPlaceholder property id as placeholderId , since before it has been shadowed via the content id.

(CMS-21968)

Headless won't Start with Deactivated P13N Extension

Due to a refactored component scan, two xml resources were not discovered anymore when the P13N extension is deactivated, which in turn caused a failed headless server start. This bugfix reinserts the missing resources.

(CMS-21843)