public void Follow(UserProfile otherUser) => FollowedUsers.Add(new UserFollower(otherUser, this));
public void Unfollow(UserProfile otherUser)
{
var followedUser = FollowedUsers.Single(f => f.UserId == otherUser.Id);
FollowedUsers.Remove(followedUser);
}
public bool HasFollowed(UserProfile otherUser) => FollowedUsers.Any(f => f.UserId == otherUser.Id);