rabbitmq_ct_helpers: Change how Mnesia/Khepri is selected

[Why]
With `khepr_db` enabled by default, we need another way to disable it to
select Mnesia instead.

[How]
For Khepri, we force the `khepri_db` feature flag. For Mnesia, we force
an empty list, meaning all stable feature flags are disabled by default.

Testsuites will have to enable whatever feature flags they need, though
they should already do that.

While here, change `rjms_topic_selector_SUITE` to only choose Khepri
without specifying any feature flags.

Author: dumbbell

Diff for: deps/rabbit/test/bindings_SUITE.erl

@@ -72,7 +72,7 @@ end_per_suite(Config) ->
 %     init_per_group_common(Group, Config, 1);
 init_per_group(khepri_migration = Group, Config) ->
     case rabbit_ct_broker_helpers:configured_metadata_store(Config) of
-        {khepri, _} ->
+        khepri ->
             {skip, "skip khepri migration test when khepri already configured"};
         mnesia ->
             init_per_group_common(Group, Config, 1)

Diff for: deps/rabbit/test/clustering_management_SUITE.erl

@@ -138,7 +138,7 @@ init_per_group(khepri_store, Config) ->
     end;
 init_per_group(mnesia_store, Config) ->
     case rabbit_ct_broker_helpers:configured_metadata_store(Config) of
-        {khepri, _} ->
+        khepri ->
             {skip, "These tests target mnesia"};
         _ ->
             Config

Diff for: deps/rabbit/test/clustering_recovery_SUITE.erl

@@ -80,7 +80,7 @@ init_per_group(khepri_store, Config) ->
     end;
 init_per_group(mnesia_store, Config) ->
     case rabbit_ct_broker_helpers:configured_metadata_store(Config) of
-        {khepri, _} ->
+        khepri ->
             {skip, "These tests target mnesia"};
         _ ->
             Config

Diff for: deps/rabbitmq_ct_helpers/src/rabbit_ct_broker_helpers.erl

@@ -215,19 +215,19 @@ setup_steps() ->
                 fun rabbit_ct_helpers:ensure_rabbitmqctl_app/1,
                 fun rabbit_ct_helpers:ensure_rabbitmq_plugins_cmd/1,
                 fun set_lager_flood_limit/1,
+                fun configure_metadata_store/1,
                 fun start_rabbitmq_nodes/1,
-                fun share_dist_and_proxy_ports_map/1,
-                fun configure_metadata_store/1
+                fun share_dist_and_proxy_ports_map/1
             ];
         _ ->
             [
                 fun rabbit_ct_helpers:ensure_rabbitmqctl_cmd/1,
                 fun rabbit_ct_helpers:load_rabbitmqctl_app/1,
                 fun rabbit_ct_helpers:ensure_rabbitmq_plugins_cmd/1,
                 fun set_lager_flood_limit/1,
+                fun configure_metadata_store/1,
                 fun start_rabbitmq_nodes/1,
-                fun share_dist_and_proxy_ports_map/1,
-                fun configure_metadata_store/1
+                fun share_dist_and_proxy_ports_map/1
             ]
     end.
 
@@ -999,57 +999,61 @@ share_dist_and_proxy_ports_map(Config) ->
 configured_metadata_store(Config) ->
     case rabbit_ct_helpers:get_config(Config, metadata_store) of
         khepri ->
-            {khepri, []};
-        {khepri, _FFs0} = Khepri ->
-            Khepri;
+            khepri;
         mnesia ->
             mnesia;
         _ ->
             case os:getenv("RABBITMQ_METADATA_STORE") of
-                "khepri" ->
-                    {khepri, []};
-                _ ->
-                    mnesia
+                "khepri" -> khepri;
+                _        -> mnesia
             end
     end.
 
 configure_metadata_store(Config) ->
     ct:log("Configuring metadata store..."),
+    Value = rabbit_ct_helpers:get_app_env(
+              Config, rabbit, forced_feature_flags_on_init, undefined),
     case configured_metadata_store(Config) of
-        {khepri, FFs0} ->
-            case enable_khepri_metadata_store(Config, FFs0) of
-                {skip, _} = Skip ->
-                    _ = stop_rabbitmq_nodes(Config),
-                    Skip;
-                Config1 ->
-                    Config1
+        khepri ->
+            ct:log("Enabling Khepri metadata store"),
+            case Value of
+                undefined ->
+                    rabbit_ct_helpers:merge_app_env(
+                      Config,
+                      {rabbit,
+                       [{forced_feature_flags_on_init,
+                         {rel, [khepri_db], []}}]});
+                _ ->
+                    rabbit_ct_helpers:merge_app_env(
+                      Config,
+                      {rabbit,
+                       [{forced_feature_flags_on_init,
+                         [khepri_db | Value]}]})
             end;
         mnesia ->
             ct:log("Enabling Mnesia metadata store"),
-            Config
+            case Value of
+                undefined ->
+                    rabbit_ct_helpers:merge_app_env(
+                      Config,
+                      {rabbit,
+                       [{forced_feature_flags_on_init,
+                         {rel, [], [khepri_db]}}]});
+                _ ->
+                    rabbit_ct_helpers:merge_app_env(
+                      Config,
+                      {rabbit,
+                       [{forced_feature_flags_on_init,
+                         Value -- [khepri_db]}]})
+            end
     end.
 
-enable_khepri_metadata_store(Config, FFs0) ->
-    ct:log("Enabling Khepri metadata store"),
-    FFs = [khepri_db | FFs0],
-    lists:foldl(fun(_FF, {skip, _Reason} = Skip) ->
-                        Skip;
-                   (FF, C) ->
-                        case enable_feature_flag(C, FF) of
-                            ok ->
-                                C;
-                            {skip, _} = Skip ->
-                                ct:pal("Enabling metadata store failed: ~p", [Skip]),
-                                Skip
-                        end
-                end, Config, FFs).
-
 %% Waits until the metadata store replica on Node is up to date with the leader.
 await_metadata_store_consistent(Config, Node) ->
     case configured_metadata_store(Config) of
         mnesia ->
             ok;
-        {khepri, _} ->
+        khepri ->
             RaClusterName = rabbit_khepri:get_ra_cluster_name(),
             Leader = rpc(Config, Node, ra_leaderboard, lookup_leader, [RaClusterName]),
             LastAppliedLeader = ra_last_applied(Leader),

Diff for: deps/rabbitmq_jms_topic_exchange/test/rjms_topic_selector_SUITE.erl

@@ -56,7 +56,7 @@ init_per_group(mnesia_store = Group, Config0) ->
 init_per_group(khepri_store = Group, Config0) ->
     Config = rabbit_ct_helpers:set_config(
                Config0,
-               [{metadata_store, {khepri, [khepri_db]}}]),
+               [{metadata_store, khepri}]),
     init_per_group_common(Group, Config);
 init_per_group(khepri_migration = Group, Config0) ->
     Config = rabbit_ct_helpers:set_config(Config0, [{metadata_store, mnesia}]),

Diff for: deps/rabbitmq_recent_history_exchange/test/system_SUITE.erl

@@ -59,8 +59,8 @@ end_per_suite(Config) ->
 
 init_per_group(mnesia_store, Config) ->
     case rabbit_ct_broker_helpers:configured_metadata_store(Config) of
-        {khepri, _} -> {skip, "These tests target Mnesia"};
-        _           -> Config
+        khepri -> {skip, "These tests target Mnesia"};
+        _      -> Config
     end;
 init_per_group(khepri_store, Config) ->
     case rabbit_ct_broker_helpers:configured_metadata_store(Config) of