Multi-entity Full Calendar Display

Changes pushed to GitLab. Please tag releases on GitLab and 

  update Packagist for rsvp-system-module and              

  rsvp-system-theme, then let me know when done.               

  Here's how Option C works — no SQL UNION, no JS timing hacks:

  The trick: hook_views_post_render receives                   

  &$display_handler->output, which IS the fullcalendar style   

  plugin's render array. By that point the style plugin has    

  already called prepareAttached() and written the FullCalendar

   event source into drupalSettings.fullcalendar['js-view-dom-i

  d-{dom_id}'].options.eventSources. We can simply append

  another array of event objects to that eventSources list

  right there in PHP.

  The FullCalendar JS then receives the combined event source —

   rsvp_event nodes from the normal view query, EventInstances

  from our hook — and renders them all on the same calendar

  grid.

  EventInstances get an fc-recurring-event CSS class so you can

   style them differently (different color, etc.) once you

  confirm it's working.

  One thing to watch: the eventinstance date__value stored as

  2026-03-03T19:00:00 will be treated as UTC and converted to

  site timezone (same as the fullcalendar module does for other

   date fields). If the events show up at wrong times after

  testing, the dates in the DB might already be in local time

  rather than UTC — easy fix, just remove the UTC→local

  conversion.