Add any_handler unit tests

The any_handler already gets good functional coverage as it is
added to the core request path in requests.cc, but we also include
this unit test with basic coverage.

src/v/kafka/server/tests/CMakeLists.txt

@@ -8,11 +8,13 @@ rp_test(
     timeouts_conversion_test.cc
     types_conversion_tests.cc
     topic_utils_test.cc
+    any_handler_test.cc
   DEFINITIONS BOOST_TEST_DYN_LINK
-  LIBRARIES Boost::unit_test_framework v::kafka
+  LIBRARIES Boost::unit_test_framework v::kafka v::coproc
   LABELS kafka
 )
 
+
 set(srcs
   consumer_groups_test.cc
   member_test.cc

src/v/kafka/server/tests/any_handler_test.cc

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2022 Redpanda Data, Inc.
+ *
+ * Use of this software is governed by the Business Source License
+ * included in the file licenses/BSL.md
+ *
+ * As of the Change Date specified in that file, in accordance with
+ * the Business Source License, use of this software will be governed
+ * by the Apache License, Version 2.0
+ */
+#include "kafka/server/handlers/details/any_handler.h"
+#include "kafka/server/handlers/handlers.h"
+
+#include <boost/test/unit_test.hpp>
+
+template<kafka::KafkaApiHandlerAny H>
+void check_any_vs_static() {
+    BOOST_TEST_INFO("Testing " << H::api::name);
+    auto hopt = kafka::handler_for_key(H::api::key);
+    BOOST_REQUIRE(hopt.has_value());
+    auto h = *hopt;
+    BOOST_CHECK_EQUAL(h->min_supported(), H::min_supported);
+    BOOST_CHECK_EQUAL(h->max_supported(), H::max_supported);
+    BOOST_CHECK_EQUAL(h->key(), H::api::key);
+    BOOST_CHECK_EQUAL(h->name(), H::api::name);
+}
+
+template<typename... Ts>
+void check_all_types(kafka::type_list<Ts...>) {
+    (check_any_vs_static<Ts>(), ...);
+}
+
+BOOST_AUTO_TEST_CASE(any_handler_all_types) {
+    check_all_types(kafka::request_types{});
+}
+
+BOOST_AUTO_TEST_CASE(any_handler_handler_for_key) {
+    // key too low
+    BOOST_CHECK(!kafka::handler_for_key(kafka::api_key(-1)).has_value());
+    // key too high
+    const auto max_key = kafka::max_api_key(kafka::request_types{});
+    BOOST_CHECK(
+      !kafka::handler_for_key(kafka::api_key(max_key + 1)).has_value());
+    // last key should be present
+    BOOST_CHECK(kafka::handler_for_key(kafka::api_key(max_key)).has_value());
+    // 34 is AlterReplicaLogDirs which we don't currently support, use it as a
+    // test case for handlers which fall in the valid range but we don't support
+    BOOST_CHECK(!kafka::handler_for_key(kafka::api_key(34)).has_value());
+}