fix(gateway): close oversized bot identify with code 4011 (#2497)

fluxer_gateway/src/session/session_manager_shard_start.erl

@@ -137,6 +137,8 @@ check_user_session_limit(
     {reply, start_reply(), state()}.
 handle_user_session_limit_result({error, too_many_sessions}, Ctx) ->
     {reply, {error, too_many_sessions}, maps:get(state, Ctx)};
+handle_user_session_limit_result({error, sharding_required}, Ctx) ->
+    {reply, {error, sharding_required}, maps:get(state, Ctx)};
 handle_user_session_limit_result(ok, Ctx) ->
     UserId = maps:get(user_id, Ctx),
     session_abuse_protection:increment_user_sessions(UserId),

fluxer_gateway/test/session_manager_shard_start_tests.erl

@@ -0,0 +1,47 @@
+%% SPDX-License-Identifier: AGPL-3.0-or-later
+
+-module(session_manager_shard_start_tests).
+-typing([eqwalizer]).
+
+-include_lib("eunit/include/eunit.hrl").
+
+build_test_state() ->
+    #{
+        sessions => #{},
+        identify_attempts => [],
+        pending_identifies => #{},
+        identify_workers => #{},
+        shard_index => 0
+    }.
+
+guild_wire(GuildId) ->
+    #{<<"id">> => integer_to_binary(GuildId)}.
+
+guild_id_for_shard(ShardId, NumShards, Offset) ->
+    ((Offset * NumShards + ShardId) bsl 22) + 1.
+
+bot_identify_data(GuildCount) ->
+    Guilds = [guild_wire(guild_id_for_shard(0, 1, I)) || I <- lists:seq(1, GuildCount)],
+    #{
+        <<"user">> => #{
+            <<"id">> => <<"123">>,
+            <<"username">> => <<"bot">>,
+            <<"discriminator">> => <<"0001">>,
+            <<"avatar">> => null,
+            <<"flags">> => 0,
+            <<"bot">> => true
+        },
+        <<"guilds">> => Guilds
+    }.
+
+start_session(Data, IdentifyData) ->
+    session_manager_shard_start:build_and_start_session(
+        Data, IdentifyData, 1, self(), <<"session-id">>, #{}, build_test_state()
+    ).
+
+build_and_start_session_rejects_oversized_bot_with_sharding_required_test() ->
+    Data = bot_identify_data(2501),
+    ?assertMatch(
+        {reply, {error, sharding_required}, _},
+        start_session(Data, #{properties => #{}, token => <<"token">>, presence => null})
+    ).