core: Add a wrapper object for attendees

Wrap ECalComponentAttendee structure in calendar's own structure to
prevent propagating the dependency on libecal types to the ui layer.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/671>

src/gcal-enums.h

@@ -66,3 +66,35 @@ typedef enum
   GCAL_TIMESTAMP_POLICY_START,
   GCAL_TIMESTAMP_POLICY_END,
 } GcalTimestampPolicy;
+
+typedef enum
+{
+  GCAL_EVENT_ATTENDEE_TYPE_INDIVIDUAL,
+  GCAL_EVENT_ATTENDEE_TYPE_GROUP,
+  GCAL_EVENT_ATTENDEE_TYPE_RESOURCE,
+  GCAL_EVENT_ATTENDEE_TYPE_ROOM,
+  GCAL_EVENT_ATTENDEE_TYPE_UNKNOWN,
+  GCAL_EVENT_ATTENDEE_TYPE_NONE,
+} GcalEventAttendeeType;
+
+typedef enum
+{
+  GCAL_EVENT_ATTENDEE_PART_NEEDS_ACTION,
+  GCAL_EVENT_ATTENDEE_PART_ACCEPTED,
+  GCAL_EVENT_ATTENDEE_PART_DECLINED,
+  GCAL_EVENT_ATTENDEE_PART_TENTATIVE,
+  GCAL_EVENT_ATTENDEE_PART_DELEGATED,
+  GCAL_EVENT_ATTENDEE_PART_COMPLETED,
+  GCAL_EVENT_ATTENDEE_PART_INPROCESS,
+  GCAL_EVENT_ATTENDEE_PART_FAILED,
+  GCAL_EVENT_ATTENDEE_PART_NONE,
+} GcalEventAttendeePartStat;
+
+typedef enum
+{
+  GCAL_EVENT_ATTENDEE_ROLE_CHAIR,
+  GCAL_EVENT_ATTENDEE_ROLE_REQUIRED,
+  GCAL_EVENT_ATTENDEE_ROLE_OPTIONAL,
+  GCAL_EVENT_ATTENDEE_ROLE_NONPARTICIPANT,
+  GCAL_EVENT_ATTENDEE_ROLE_NONE,
+} GcalEventAttendeeRole;