Event attachment improvements for Google Calendar web and API
Event attachments allow people using Google Calendar to attach meeting notes, presentations, or any other relevant files from Google Drive to events and make them available for all event attendees.
Previously a Calendar Labs feature, event attachments are now fully launching in Google Calendar web by default with today’s rollout. The ‘Add attachment’ link will appear in all Google Calendar events moving forward, except for those domains whose admins have disabled Google Drive.
Drive will also start checking if all event invitees have access to attached files―and if not, ask if you’d like to grant them access―saving the hassle of sharing each attached document with every attendee.
In addition, developers can now add Drive files to Google Calendar events created through the Calendar API.
Rapid release, with Scheduled release coming in two weeks
Reference by Google