{% assign postsByProject = site.posts | group_by_exp: “post”, “post.project_id” %}

{

"data": [
{% for project in postsByProject %}
    {
        "project_title": "{{ project.items[0].project_title }}",
        "project_id": "{{ project.name }}",
        "project_code": "{{ project.items[0].project_code }}",
        "date_published": "{{ project.items[0].date | date_to_rfc822 }}",
        "project_urls": {{ project.items[0].project_urls | jsonify }},
        "items": [
        {% for item in project.items %}
            {{ item | strip_fields_from_document: 'next,previous,output' | jsonify}}{% unless forloop.last %},{% endunless %}
        {% endfor %}
        ]
    }{% unless forloop.last %},{% endunless %}
{% endfor %}
],
"status": "OK",
"last_updated": "{{ 'now' | date_to_rfc822 }}"

}