PowerPoint2007 Writer : A comment inside a group is related but never written

[dkulyk]

Description

A Comment that sits inside a Group is written as a relationship to a part that is never written.

Writer\PowerPoint2007\PptSlides walks a slide with flattenShapes(), so it finds the comment and
writes ppt/slides/_rels/slideN.xml.rels with a relationship of type .../comments pointing at
../comments/commentN.xml. The four writers that were to answer for that relationship walk
getShapeCollection() flat instead and never see the comment:

writer	what it did not do
PptComments	write ppt/comments/commentN.xml
ContentTypes	declare the Override for that part
CommentAuthors	write ppt/commentAuthors.xml
Relationships	relate the author list from the presentation

So the package goes out holding a relationship whose target is not in it.

Steps to reproduce

$presentation = new PhpPresentation();
$group = new Group();
$group->addShape(new Comment());
$presentation->getActiveSlide()->addShape($group);

(new PowerPoint2007($presentation))->save('group-comment.pptx');

Expected behavior

ppt/comments/comment1.xml is in the package, its content type is declared, and the author list is
written and related.

Current behavior

ppt/slides/_rels/slide1.xml.rels names ../comments/comment1.xml, and no such part exists.
PowerPoint asks to repair the file on open.

The same comment placed directly on the slide is written correctly, so only a comment inside a group
is affected. A group can hold a group, so the nesting is not one deep.