anchor.diff:  
   % op logic callbacks
   -export([op_logic_plugin/0]).
  --export([operation_supported/3]).
  +-export([
  +    operation_supported/3,
  +    data_spec/1,
  +    fetch_entity/1,
  +    exists/2,
  +    authorize/2,
  +    validate/2
  +]).
   -export([create/1, get/2, update/1, delete/1]).
  --export([authorize/2, data_signature/1]).
   
   -define(to_binaries(__List), [list_to_binary(V) || V <- __List]).
   
  
positive.code: %%--------------------------------------------------------------------
  -spec get(op_logic:req(), op_logic:entity()) -> op_logic:get_result().
  get(#op_req{gri = #gri{aspect = configuration}}, _) ->
      {ok, gather_configuration()};
  
  get(_, _) ->
      ?ERROR_NOT_SUPPORTED.
  
  
  %%--------------------------------------------------------------------
  
negative.code: operation_supported(get, configuration, private) -> true;
  
  operation_supported(_, _, _) -> false.
  
  
  %%--------------------------------------------------------------------
  %% @doc
  %% Returns data signature for given request.
  %% Returns a map with 'required', 'optional' and 'at_least_one' keys.
  %% Under each of them, there is a map:
  %%      Key => {type_constraint, value_constraint}
  %% Which means how value of given Key should be validated.
  %% @end
  %%--------------------------------------------------------------------
  -spec data_spec(op_logic:req()) -> op_sanitizer:data_spec().
  data_spec(#op_req{operation = get, gri = #gri{aspect = configuration}}) ->
      #{}.
  
  
  %%--------------------------------------------------------------------
  %% @doc
  %% Retrieves an entity from datastore based on its EntityId.
  %% Should return ?ERROR_NOT_FOUND if the entity does not exist.
  %% @end
  %%--------------------------------------------------------------------
  fetch_entity(_) ->
      {ok, undefined}.
  
  
  %%--------------------------------------------------------------------
  %% @doc
  %% Determines if given resource (aspect of entity) exists, based on
  %% op logic request and prefetched entity.
  %% @end
  %%--------------------------------------------------------------------
  exists(_, _) ->
      true.
  
  
  %%--------------------------------------------------------------------
  %% @doc
  %% Determines if requesting client is authorized to perform given operation,
  %% based on op logic request and prefetched entity.
  %% @end
  %%--------------------------------------------------------------------
  -spec authorize(op_logic:req(), entity_logic:entity()) -> boolean().
  authorize(#op_req{operation = get, gri = #gri{aspect = configuration}}, _) ->
      true.
  
  
  %%--------------------------------------------------------------------
  %% @doc
  %% Determines if given request can be further processed
  %% (e.g. checks whether space is supported locally).
  %% Should throw custom error if not (e.g. ?ERROR_SPACE_NOT_SUPPORTED).
  %% @end
  %%--------------------------------------------------------------------
  validate(#op_req{operation = get, gri = #gri{aspect = configuration}}, _) ->
      ok.
  
  
  %%--------------------------------------------------------------------
  