[andystaples]

Summary

• Propose deferring new default-serializer types and unsupported cases to a breaking major release, with exceptions for security fixes and repairs to already-supported behavior.
• Document current JsonDataConverter behavior, replay risks, and application-defined hooks and custom converters.
• Add contributor and pull-request guidance for assessing serialization compatibility.

Related to #354, #346, and #310.

[Copilot]

🟢 Approval recommended

No active review issues remain for this documentation-only update to serialization compatibility and replay-safety guidance.

No open issues 🎉

What changed in this PR

This documentation-only PR proposes a serialization compatibility policy for the Durable Task SDK and its providers, emphasizing replay safety between major releases. It also documents current converter behavior without changing runtime functionality.

Changes:

• Proposes deferring new default-serializer support to major releases, with exceptions for security fixes and repairs to documented behavior.
• Documents reconstruction support, replay risks, and application-defined hooks and converters.
• Adds contributor guidance and a pull-request checklist for serialization compatibility.

File	Description
README.md	Links to the serialization and replay guide.
docs/​supported-patterns.md	Clarifies custom-object serialization and reconstruction guidance.
docs/​serialization.md	Documents the proposed policy, current support, and customization options.
CONTRIBUTING.md	Adds compatibility assessment and replay-mitigation requirements.
CHANGELOG.md	Links the existing replay warning to the new guide.
.github/​PULL_REQUEST_TEMPLATE.md	Adds a serialization compatibility checklist item.
.github/​copilot-instructions.md	Adds serialization compatibility review guidance.

_{Review effort: Balanced}