code: function makeFittings(char) {
      let fittings = function (id) {
          if (id === undefined) {
              return char.agent.request('get_characters_character_id_fittings', { path: { character_id: char.id } }, char.ssoToken);
          }
          else {
              return new FittingImpl(char, fittings, id);
          }
      };
      fittings.add = function (fitting) {
          return char.agent.request('post_characters_character_id_fittings', { path: { character_id: char.id }, body: fitting }, char.ssoToken)
              .then(newID => newID.fitting_id);
      };
      return fittings;
  }
docs: Create a new {@link Fittings} instance that uses the given character agent to
  make its HTTP requests to the ESI interface.
  
  @param char The character access information
  @returns An Fittings API instance