Fix DeprecationWarning when encoding StripeObject metadata (fixes #1651) (#1687)

* Fix DeprecationWarning when encoding StripeObject metadata (fixes #1651)

* Suppress deprecation warnings during internal encoding to fix metadata updates

* Use getattr for id access to avoid stripe_id deprecation warning

* Handle None id values correctly in encoding

* Simplify to check hasattr(value, id) directly

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Co-authored-by: Ramya Rao <100975018+ramya-stripe@users.noreply.github.com>