Remove type and optionality constraints from @continuationToken decorator

[Copilot]

The @continuationToken decorator enforced that properties be of type string, preventing nullable types like string | null and rejecting non-string types entirely. This constraint was unnecessarily restrictive for pagination patterns.

Changes

• packages/compiler/src/lib/paging.ts: Removed validation function from continuationTokenDecorator that enforced string type requirement
• packages/compiler/test/decorators/paging.test.ts: Added tests covering nullable types, optional properties, and non-string types

Usage

The decorator now accepts any type without validation:

model ListPageInfo {
  @pageItems items: string[];
  
  // Now supported: nullable non-optional
  @continuationToken endCursor: string | null;
  
  // Already worked, still works: optional
  @continuationToken token?: string;
  
  // Now supported: non-string types
  @continuationToken offset: int32;
}

Backward compatible - all existing usage continues to work unchanged.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Bug]: Continuation token must allow nullable non optional fields</issue_title>
<issue_description>### Describe the bug

Currently @continuationToken supports only string type for the field. Like this.

model ListPageInfo {
    startCursor?: string;

    @continuationToken
    endCursor?: string;

    hasNext: boolean;
    hasPrev: boolean;
}

While having optional field is fine, for typescript case, to enforce more consistent typing I prefer to make fields nullable instead, therefore compiler would highlight missing expected nullable field.

Therefore @continuationToken should support more than field optionality way of representing the token which might be or might not be, but the field is always present otherwise.

Reproduction

model ListPageInfo {
    startCursor?: string;

    @continuationToken
    endCursor: string | null;

    hasNext: boolean;
    hasPrev: boolean;
}

decorator gives:
Cannot apply continuationToken decorator to string | null since it is not assignable to stringTypeSpec(decorator-wrong-target)

Checklist

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.
• The provided reproduction is a minimal reproducible example of the bug.</issue_description>

<agent_instructions>Remove the constraint that requires the target property of @continuationToken to be a string and the constraint that requires it to be a required property. Correct any tests and add new tests to verify that an optional property cna be marked with this decorator.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@timotheeguerin This feels resonable, not sure it should even force it to be a string

• Fixes [Bug]: Continuation token must allow nullable non optional fields #9044

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commit: dd33b6f