anchor.diff:     tts_data:user_get_pid(ID). 
   
   delete_user(ID) ->
  -    tts_data:user_delete(ID),
  -    ok.
  +    tts_data:user_delete(ID).
  +
  
positive.code: get_user(UserSubject, Issuer) ->
      load_or_return_user(#{ sub => UserSubject, iss => Issuer}).
  
  -spec user_shutting_down(ID :: binary()) -> ok.
  user_shutting_down(ID) ->
      gen_server:call(?MODULE,{delete_user,ID}).
  
  %% gen_server.
  
  
negative.code: %% API.
  -export([start_link/0]).
  -export([get_user/2]).
  -export([user_wants_to_shutdown/1]).
  
  %% gen_server.
  -export([init/1]).
  