INTEG-329: [integ-calendar] Wrong link of event activities in some cases

Problem analysis:
* When an event is created outside space's calendar page, its activity link is wrong.
  It always takes the page where the event was created.

Fix description:
* New method getEventPreviewLinkInSpace retrieves the URL of space's calendar page, then appending other values for event preview.
  Wherever an event is created (from Quick Creation menu, or intranet's calendar, or space's calendar page), the activity URL is the same.