anchor.diff:                      chosen_provider = proplists:get_value(
                           chosen_provider, Proplist, ChosenProvider),
                       client_tokens = proplists:get_value(
  -                        client_tokens, Proplist, ClientTokens)},
  -                DocNew = Doc#document{value = NewUser},
  -                {ok, _} = onedata_user:save(DocNew),
  -                ok
  -        end
  -    catch
  -        T:M ->
  -            {error, {T, M}}
  +                        client_tokens, Proplist, ClientTokens)}
  +                }
  +            end),
  +            ok
       end.
   
   
  
positive.code:     ok | {error, Reason} when
      Reason :: disallowed_alias_prefix | invalid_alias | alias_occupied | any().
  modify(UserId, Proplist) ->
      try
          {ok, #document{value = UserRecord} = Doc} = onedata_user:get(UserId),
          #onedata_user{
              name = Name,
              alias = Alias,
              email_list = Emails,
  
negative.code:             default_provider = DefaultProvider,
              chosen_provider = ChosenProvider,
              client_tokens = ClientTokens
          }}} = onedata_user:get(UserId),
  
      SetAliasResult = case proplists:get_value(alias, Proplist, Alias) of
          Alias ->
              % Alias did not change or was changed to the same value
              ok;
          NewAlias ->
              % New alias requested, try to set it
              set_alias(UserId, NewAlias)
      end,
  
      case SetAliasResult of
          {error, Reason} ->
              % Alias not allowed, return error
              {error, Reason};
          ok ->
              % Alias ok, update user doc
              {ok, _} = onedata_user:update(UserId, fun(User) ->
                  {ok, User#onedata_user{
                      name = proplists:get_value(name, Proplist, Name),
                      % Alias is already updated
                      email_list = proplists:get_value(
                          email_list, Proplist, Emails),
                      connected_accounts = proplists:get_value(
  