feat: normalize event text fields and show date range for multiday events

[late4marshmellow]

Summary

Replaces the shallow ensureString helper with a recursive normalizeEventText function that safely handles nested objects, arrays, and circular references — covering all event text fields including title, which was previously unguarded.

Also changes innerHTML assignments for description and location to textContent to prevent XSS from malformed calendar payloads.

Problem

Some calendar providers (e.g. certain Outlook/iCloud payloads) wrap event fields in nested objects, yielding [object Object] when stringified. The old ensureString only handled description and location, and was not recursive. Event title had no protection.

Changes

• Replace ensureString with normalizeEventText(val, depth=0):
  • Handles null/undefined → ""
  • Handles arrays by joining non-empty normalized elements with ,
  • Tries a preferred key list (value, text, name, title) for plain objects before JSON.stringify fallback
  • Depth limit (10) guards against circular references
• Apply normalizeEventText to title, description, and location in renderEvent, renderEventJournal, and renderEventAgenda
• Apply to e.dataset.title
• Change description and location render sites from innerHTML to textContent

[late4marshmellow]

Backward compatibility note (re: renderEventAgenda changes)

The new showMultidayEventsOnce branch is fully backward compatible with MMM-CalendarExt3 users.

MMM-CalendarExt3 calls renderEventAgenda as:

const eDom = renderEventAgenda(event, options, moment)

Why this lives in CX3_Shared and not in MMM-CalendarExt3Agenda's own scripts:

The multiday time display is built entirely inside renderEventAgenda — it constructs and appends the DOM nodes for startTime/endTime. MMM-CalendarExt3Agenda only calls renderEventAgenda and receives a finished DOM element back. There is no hook to intercept or modify the time portion after the fact without patching into the returned DOM — which would be fragile. Placing the logic here, behind an explicit opt-in option, keeps it clean and self-contained.

The new behavior only activates when a consuming module explicitly passes showMultidayEventsOnce: true, as MMM-CalendarExt3Agenda does via PR MMRIZE/MMM-CalendarExt3Agenda#87.

[KristjanESPERANTO]

Thanks! I'm building a new release :-)