anchor.diff:  -spec error_model() -> onepanel_parser:object_spec().
   error_model() ->
       #{
  -        %% The name of an error type.
  -        error => string,
  -        %% The detailed error description.
  -        description => string
  +        error => {error_error_model(), optional}
  +    }.
  +
  +%%--------------------------------------------------------------------
  +%% @doc Object describing an error.
  +%% @end
  +%%--------------------------------------------------------------------
  +-spec error_error_model() -> onepanel_parser:object_spec().
  +error_error_model() ->
  +    #{
  +        %% String identifying the error type. Does not change between error
  +        %% instances.
  +        id => string,
  +        %% Human readable error description. May contain information specific to
  +        %% given error instance.
  +        description => string,
  +        %% Details about the error instance. The object schema is specific to
  +        %% each error type.
  +        details => {#{}, optional}
       }.
   
   %%--------------------------------------------------------------------
  
positive.code:     emergency_passphrase_change_request_model/0,
      emergency_passphrase_status_model/0,
      error_model/0,
      gui_message_model/0,
      host_model/0,
      host_add_request_model/0,
  
negative.code:         steps => [string],
          %% Total number of steps to be executed.
          totalSteps => integer,
          error => {error_model(), optional}
      }.
  
  %%--------------------------------------------------------------------
  