Create new content button does not work in case XPages are used

Validation which is added to org.onehippo.cms.channelmanager.content.document.DocumentsServiceImpl#createDocument() method always fails in case XPages are used.

if (!xPageSelection && folder.isNodeType(HippoStdNodeType.NT_XPAGE_FOLDER)) {
                throw new BadRequestException(new ErrorInfo(Reason.FOLDER_IS_AN_X_PAGE_FOLDER));
 }

xPageSelection attribute is always false in case when Content Button (tag) is used and there is no way to set it. This works when NavApp is used for example. An easy fix would be to add additional attribute (xPageSelection) to the Content Button tag.

NOTE: bug is introduced in 15.4.0 version