Once https://github.com/elastic/elasticsearch/issues/98503 is done, we can use our minimum version numbers in the SystemIndexMappingUpdate service instead of the old `Version` types. Mappings will be updated for a system index when all nodes have a matching descriptor mappings version for a system index, but this version is greater than what's stored in the mappings metadata.
server/src/test/java/org/elasticsearch/indices/SystemIndexMappingUpdateServiceTests.java
meta.field(SystemIndexDescriptor.VERSION_META_KEY, 5);
        }));
    }
    
    private static XContentBuilder getMappings(int version) {
        return getMappings(builder -> builder.object("_meta", meta -> meta.field("version", version)));
    }
    private static XContentBuilder getMappings(CheckedConsumer<XContentBuilder, IOException> metaCallback) {
        try {
            final XContentBuilder builder = jsonBuilder();
            builder.startObject();
            {
                metaCallback.accept(builder);
                builder.field("dynamic", "strict");
                builder.startObject("properties");
                {
                    builder.startObject("completed");
                    builder.field("type", "boolean");
                    builder.endObject();
                }
                builder.endObject();
            }
            builder.endObject();
            return builder;
        } catch (IOException e) {
            throw new UncheckedIOException("Failed to build " + SYSTEM_INDEX_NAME + " index mappings", e);
        }
    }
}