public async Task AddFriendToCharacterAsync(Character character, Character friend)
{
if (_characterRepository.HasFriendAlready(character, friend))
{
throw new InvalidOperationException($"{friend?.Name} is already friend of {character.Name}");
}
if (character.Id == friend.Id)
{
throw new InvalidOperationException($"Cannot add friend of myself");
}
_characterRepository.AddFriendToCharacter(character, friend);
await _characterRepository.SaveChangesAsync();
}