Fix an oversized alloc in cluster_config schema endpoint

bazel/repositories.bzl

@@ -167,9 +167,9 @@ def data_dependency():
     http_archive(
         name = "seastar",
         build_file = "//bazel/thirdparty:seastar.BUILD",
-        sha256 = "948e5f8ad769114a4721c81d5829f675ac51482e4a9a106d57ab313104308666",
-        strip_prefix = "seastar-4350d7960ec5ac8a1cf9274316c8f1ab1896d24e",
-        url = "https://github.com/redpanda-data/seastar/archive/4350d7960ec5ac8a1cf9274316c8f1ab1896d24e.tar.gz",
+        sha256 = "6451633c3a4c0422845f441994fe87d1f5a3caabf3e9d4abec733e47bfbed896",
+        strip_prefix = "seastar-4a3406ce4071f0bc472233c4c669582ca527db89",
+        url = "https://github.com/redpanda-data/seastar/archive/4a3406ce4071f0bc472233c4c669582ca527db89.tar.gz",
         patches = ["//bazel/thirdparty:seastar-fortify-source.patch"],
         patch_args = ["-p1"],
     )

src/v/redpanda/admin/cluster_config_schema_util.cc

@@ -12,6 +12,8 @@
 
 #include "redpanda/admin/api-doc/cluster_config.json.hh"
 
+#include <seastar/json/json_elements.hh>
+
 // This is factored out to make it a separate binary that can generate schema
 // without bringing up a redpanda cluster. Down stream tools can make use of
 // this for config generation.
@@ -81,5 +83,5 @@ util::generate_json_schema(const config::configuration& conf) {
 
     std::map<ss::sstring, property_map> response = {
       {ss::sstring("properties"), std::move(properties)}};
-    return ss::json::json_return_type(std::move(response));
+    return ss::json::stream_object(std::move(response));
 }