SOC-4114 [Space Member Management] Auto-complete suggestion should contain the full name when inviting users into space

Fix description:
* Add a list to contain user's full names to PeopleRestService.UserNameList.
* Return a list of full names along with usernames when calling /social/people/suggest.{format} with query parameter &typeOfRelation=user_to_invite.
* Use fullNames Array to build search result list.