Fix ObjectSerializer to preserve baseName-keyed fields during serialize

[Copilot]

Ports the fix from kubernetes-client/javascript#3016: ObjectSerializer.serialize always read source values via data[attributeType.name] (the TS property name), silently dropping values when input data is keyed by the API baseName instead — e.g. raw/parsed data containing x-kubernetes-preserve-unknown-fields.

// Before: value is lost if `data` only has the baseName key
instance[attributeType.baseName] = ObjectSerializer.serialize(
    data[attributeType.name], attributeType.type, attributeType.format
);

// After: falls back to baseName when `name` isn't an own property
const value = Object.prototype.hasOwnProperty.call(data, attributeType.name)
    ? data[attributeType.name]
    : data[attributeType.baseName];
instance[attributeType.baseName] = ObjectSerializer.serialize(
    value, attributeType.type, attributeType.format
);

Templates

• modules/openapi-generator/src/main/resources/typescript/model/ObjectSerializer.mustache — used by typescript, typescript-fetch, typescript-axios, typescript-rxjs, and related generators.
• modules/openapi-generator/src/main/resources/typescript-node/models.mustache — used by the legacy typescript-node generator.

Generated samples/fixtures

• Updated all 21 affected generated files under samples/ and the integration test fixture under modules/openapi-generator/src/test/resources/integrationtests/typescript/objectsWithEnums-expected to match the template change.
• Regeneration was done by hand-applying the identical template diff to each output, since running ./bin/generate-samples.sh requires a Maven build (./mvnw ... clean package) and the sandbox lacked network access to fetch Maven/dependencies. The resulting diffs mirror what the updated templates would produce.