anchor.diff:      GroupNew = Group#user_group{spaces = [SpaceId | Spaces]},
       dao_adapter:save(GroupDoc#db_document{record = GroupNew}),
   
  +    add_space_to_providers(SpaceId, Providers),
  +
       op_channel_logic:space_modified(Providers, SpaceId, Space),
       op_channel_logic:group_modified(Providers, GroupId, Group),
       lists:foreach(fun({UserId, _}) ->
           op_channel_logic:user_modified(Providers, UserId, dao_adapter:user(UserId))
       end, Users),
       {ok, SpaceId}.
  +
  +
  +%%--------------------------------------------------------------------
  +%% @doc Adds a space to providers' support list.
  +%% @end
  +%%--------------------------------------------------------------------
  +-spec add_space_to_providers(SpaceId :: binary(), ProviderIds :: [binary()])
  +        -> ok.
  +add_space_to_providers(_SpaceId, []) -> ok;
  +add_space_to_providers(SpaceId, [ProviderId | RestProviders]) ->
  +    ProviderDoc = dao_adapter:provider_doc(ProviderId),
  +
  +    #db_document{record = #provider{spaces = PSpaces} = Provider} = ProviderDoc,
  +    ProviderNew = Provider#provider{spaces = [SpaceId | PSpaces]},
  +    dao_adapter:save(ProviderDoc#db_document{record = ProviderNew}),
  +
  +    add_space_to_providers(SpaceId, RestProviders).
  +
   
   %%--------------------------------------------------------------------
   %% @doc Removes the space if empty.
  
positive.code:     UserNew = User#user{spaces = [SpaceId | Spaces]},
      dao_adapter:save(UserDoc#db_document{record = UserNew}),
  
      op_channel_logic:space_modified(Providers, SpaceId, Space),
      op_channel_logic:user_modified(Providers, UserId, UserNew),
      {ok, SpaceId};
  
negative.code:             #db_document{record = #space{size = Size, users = Users, groups = Groups, providers = Providers} = Space} = SpaceDoc,
              SpaceNew = Space#space{size = [{ProviderId, SupportedSize} | Size], providers = [ProviderId | Providers]},
  
              add_space_to_providers(SpaceId, [ProviderId]),
  
              dao_adapter:save(SpaceDoc#db_document{record = SpaceNew}),
  
              op_channel_logic:space_modified([ProviderId | Providers], SpaceId, SpaceNew),
              lists:foreach(fun({UserId, _}) ->
                  op_channel_logic:user_modified([ProviderId], UserId, dao_adapter:user(UserId))
  