kafka: ignore case in parse_and_set_bool()

Kafka ignores case when setting a boolean property:
https://github.com/apache/kafka/blob/master/clients/src/main/...
...java/org/apache/kafka/common/config/ConfigDef.java#L690-L710

Realign ourselves with Kafka by transforming the string value to
lowercase before parsing it in `parse_and_set_bool()`.

src/v/kafka/server/handlers/configs/config_utils.h

@@ -34,6 +34,7 @@
 
 #include <absl/container/node_hash_set.h>
 
+#include <algorithm>
 #include <optional>
 
 namespace kafka {
@@ -627,10 +628,18 @@ inline void parse_and_set_bool(
 
     if (op == config_resource_operation::set && value) {
         try {
-            property.value = string_switch<bool>(*value)
+            // Ignore case.
+            auto str_value = std::move(*value);
+            std::transform(
+              str_value.begin(),
+              str_value.end(),
+              str_value.begin(),
+              [](const auto& c) { return std::tolower(c); });
+
+            property.value = string_switch<bool>(str_value)
                                .match("true", true)
                                .match("false", false);
-            auto v_error = validator(tn, *value, property.value);
+            auto v_error = validator(tn, str_value, property.value);
             if (v_error) {
                 throw validation_error{*v_error};
             }

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

@@ -1053,3 +1053,33 @@ FIXTURE_TEST(
           describe_resp);
     }
 }
+
+FIXTURE_TEST(
+  test_shadow_indexing_uppercase_alter_config, alter_config_test_fixture) {
+    wait_for_controller_leadership().get();
+    model::topic test_tp{"topic-1"};
+    create_topic(test_tp, 6);
+    using map_t = absl::flat_hash_map<
+      ss::sstring,
+      std::pair<std::optional<ss::sstring>, kafka::config_resource_operation>>;
+    map_t properties;
+    // Case is on purpose.
+    properties.emplace(
+      "redpanda.remote.write",
+      std::make_pair("True", kafka::config_resource_operation::set));
+    properties.emplace(
+      "redpanda.remote.read",
+      std::make_pair("TRUE", kafka::config_resource_operation::set));
+
+    auto resp = incremental_alter_configs(
+      make_incremental_alter_topic_config_resource_cv(test_tp, properties));
+
+    BOOST_REQUIRE_EQUAL(resp.data.responses.size(), 1);
+    BOOST_REQUIRE_EQUAL(
+      resp.data.responses[0].error_code, kafka::error_code::none);
+    auto describe_resp = describe_configs(test_tp);
+    assert_property_value(
+      test_tp, "redpanda.remote.write", "true", describe_resp);
+    assert_property_value(
+      test_tp, "redpanda.remote.read", "true", describe_resp);
+}