Exercise 2: Confirming the Cascade — Possible Solution
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SETUP
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Three real pages:
  id: 1, slug: 'java', fullPath: 'programming/java', parentId: <programming's id>
  id: 2, slug: 'fundamentals', fullPath: 'programming/java/fundamentals', parentId: 1
  id: 3, slug: 'chapter-1', fullPath: 'programming/java/fundamentals/chapter-1', parentId: 2

MOVING java UNDER A NEW PARENT
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await movePage(1, <'reference' page's own id>);

WHAT HAPPENS
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movePage() first updates page 1's own fullPath to
'reference/java' (or whatever the new parent's own path is, plus
'java'), then calls updateDescendantPaths(1).

updateDescendantPaths(1) finds page 2 as a child of page 1, rebuilds
its fullPath as 'reference/java/fundamentals' using page 1's own
now-updated fullPath, saves it, then recurses into
updateDescendantPaths(2) - which finds page 3, rebuilds its fullPath
as 'reference/java/fundamentals/chapter-1', and saves it too.

CONFIRMATION
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All three pages now have fullPath values reflecting the new
'reference/java/...' branch, not just the directly-moved page 1 -
the cascade reached every descendant, not only the immediate child.

WHY THIS WORKS AS AN ANSWER
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It correctly traces movePage()'s own two-step process (updating the
moved page, then recursing through updateDescendantPaths()), and
correctly shows the cascade reaching all the way down to a
grandchild page, not stopping at the first level.