Added/Invited users & ICS

[Semir1212]

HH 1.15.3
Calendar 1.5.7

When marking the checkbox "Add all space members to event.." the users are "added" to the event, regardless of the status used (invited, participating). When users are selected via the user picker they are "invited". The notifications a user receives will also reflect this distinction.

• When all space members are added with the status "Participating" the notification should stay the same
• When all space members are added with the status "Invited" they should receive a notification that they were invited and not added
• I both cases the ICS should be included in the email

[yurabakhtin]

@Semir1212 @luke- PR #446.