[php-nextgen] Add anyof Support

[ckoegel]

Follow up to #23985
This PR adds support for anyOf models with and without discriminators. It copies the implementation from the oneOf model and updates some of the naming/logic to refer to Composed instead of oneOf or anyOf specifically.

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---

Summary by cubic

Adds anyOf support to the PHP Nextgen generator by introducing AnyOfInterface and generated dispatcher models, and updates ObjectSerializer to reliably dispatch oneOf/anyOf with safer JSON decoding. Samples, docs, and tests are regenerated, including new petstore anyOf models.

• New Features

  • Generate anyOf dispatcher models via model_anyof.mustache; add AnyOfInterface and register it in PhpNextgenClientCodegen.
  • Add deserializeAnyOf() and dispatch for both OneOfInterface and AnyOfInterface in ObjectSerializer; dispatch runs after json_decode and before array-to-object casting.
  • Update model docs to list anyOf members and discriminator selection; skip per-property test stubs for composed models; add petstore Reptile, Smoothie, Lizard, Snake; regenerate echo and petstore samples; add anyOf polymorphism tests.

• Bug Fixes

  • Preserve original strings when JSON decode fails (including the "null" literal); catch Throwable during deserialization; tighten composed-type validation.

^{Written for commit 9add223. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 35 files

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[cubic-dev-ai]

All reported issues were addressed across 5 files (changes from recent commits).

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[wing328]

What about keeping the OneOfInterface and adding a AnyOfInterface instead?

Renaming OneOfInterface to ComposedInterface is a breaking change if I'm not mistaken.

For other generators we do maintain separate implementations (mustache files) for anyOf and oneOf.

[ckoegel]

I'm definitely not opposed to splitting them out, I implemented it this way since the two are so similar to avoid some more duplication. But if we want to match some of the other generators we can definitely migrate to 2 separate models.

This is technically breaking, but the original oneOf implementation hasn't been released yet, so the only people this would break is those using 7.24.0-SNAPSHOT. If that's an issue then we can definitely break these out into oneOf/anyOf. Let me know and I can start on that

[wing328]

@coffeemakr can you please also review this change when you've time since this is a follow-up PR to #23985 authored by you?

[wing328]

Personally I prefer making the implementation more consistent to other generators. In addition, the term Composed may not be familiar to developers who just start using OpenAPI in their workflow.

[ckoegel]

Sounds good, I'll get started on this rn

[ckoegel]

@wing328 I think this should be all set now, its now split into OneOfInterface and AnyOfInterface, I did leave "Composed" in the ClientCodegen, which shouldn't be breaking and won't ever be seen by users, but lmk if I need to split that out as well.

[wing328]

also cc @coffeemakr @JulianVennen (top contributors to php-nextgen client generator)

[cubic-dev-ai]

All reported issues were addressed across 36 files

<sub>Tip: cubic can generate docs of your entire codebase and keep them up to date. Try it here.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 4 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[wing328]

thanks for the PR and incorporating the feedback