designtopack/public/site/templates/projects.json.php

<?php
$children = $page->children()->filter(function ($child) {
  return kirby()->user()->role() === 'admin' || $child->managers()->toUsers()->has(kirby()->user());
})->map(function ($child) {  
  return [
    'title' => $child->title()->value(),
    'url' => $child->url(),
    'uri' => '/' . $child->uri(),
    'modified' => $child->modified('Y-MM-d'),
    'currentStep' => $child->currentStep()->value(),
    'status' => $child->status(),
    'logo' => $child->client()->toPage()->logo()->toFile()->url(),
  ];
})->values();


$specificData = [
  "children" => $children,
];

$pageData = array_merge($genericData, $specificData);

echo json_encode([
  "page" => $pageData,
  "user" => $userData
]);