FIX: improvements for download local dates (PR #14588)

  • Remove download link for past dates
  • PostId is not necessary and will make the solution more generic for dates which doesn’t belong to a specific post
  • ICS file can be generated in JavaScript to avoid calling backend
  • Trim title in case it contains blank spaces


@davidtaylorhq could you take a look? I think that the best way to review is to look on individual commits as they are logically structured :slight_smile: