Use cached affiliations in GraphQL MUC Light tests

Manual checks revealed 59 DB queries instead of 131.
This means that both the DB query and the cache lookup are tested.

Author: chrzaszcz

big_tests/tests/graphql_muc_light_SUITE.erl

@@ -9,7 +9,7 @@
                          get_coercion_err_msg/1, make_creds/1, get_unauthorized/1,
                          get_err_code/1, get_not_loaded/1]).
 
--import(config_parser_helper, [mod_config/2]).
+-import(config_parser_helper, [config/2]).
 
 -include_lib("common_test/include/ct.hrl").
 -include_lib("jid/include/jid.hrl").
@@ -209,12 +209,15 @@ end_per_suite(Config) ->
     escalus:end_per_suite(Config).
 
 required_modules(_) ->
-    Backend = mongoose_helper:mnesia_or_rdbms_backend(),
-    MucLightOpts = mod_config(mod_muc_light, #{backend => Backend,
-                                               rooms_in_rosters => true,
-                                               config_schema => custom_schema()}),
+    MucLightOpts = config([modules, mod_muc_light], muc_light_opts()),
     [{mod_muc_light, MucLightOpts}].
 
+muc_light_opts() ->
+    #{backend => mongoose_helper:mnesia_or_rdbms_backend(),
+      cache_affs => #{},
+      rooms_in_rosters => true,
+      config_schema => custom_schema()}.
+
 custom_schema() ->
     %% Should be sorted
     [{<<"background">>, <<>>, background, binary},