feat: add v5.6.0 package updates

[onesignal-deploy]

Release v5.6.0

🐛 Bug Fixes

• fix: correct update_subscription_by_token examples and gate C# enum precedence on missing spec example

📚 Docs

• docs: enrich spec with example: values on path/query params
• docs: add idiomatic error-handling stubs to DefaultApi.md examples
• docs: demonstrate polymorphic response handling for POST /notifications
• docs: fix polymorphic createNotification example correctness across SDKs
• docs: demonstrate idempotency_key on POST /notifications hero example
• docs: add common-patterns preamble to each SDK's DefaultApi.md
• docs: revise common-patterns preamble per-language and drop jargon
• docs: revise preamble wording per PR #392 review feedback
• docs: correct preamble auth claim + Go error-handling pointer prose
• docs: tighten preamble error-handling section (Go nil-check + 4th envelope shape)

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Generated from OneSignal/api-client-libraries@3b35d43...9aba042.

[onesignal-deploy]

Superseded by v5.6.0 release.