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## 4.20.0

**`(feat):`** Object types with xml encoding metadata (e.g. TwiML defined via OpenAPI `xml` objects) now
implement `XmlSerializable` with `toXml()` and a static `fromXml(String)` parser, backed by new
core `XmlWriter`/`XmlReader` utilities. Builders gain per-child-element methods
(e.g. `Response.builder().say(...)`) and undiscriminated child unions dispatch `fromXml` by
element name. `Builder.fromXml(String)` returns a populated builder, unknown child elements are
preserved as `XmlElement`s (readable via `getAdditionalChildren()`, addable via `addChild(...)`)
and round-tripped by `toXml()`, and very large objects that use a builder-based constructor also
get `fromXml`. Types without xml metadata are unchanged.