feat(client): support custom claims in PrivateKeyJwtProvider

[JosephDoUrden]

Summary

Expose the existing claims parameter from createPrivateKeyJwtAuth in the PrivateKeyJwtProviderOptions interface, allowing custom claims to be included in the JWT client assertion.

Closes #1477

Motivation

Enterprise deployments often need additional claims in the client assertion JWT (e.g., tenant_id, role) to scope the access token with finer granularity than scopes alone allow. Currently, users must either:

• Use StaticPrivateKeyJwtProvider and manage JWT signing themselves (adding jose as a direct dependency and re-implementing audience discovery)
• Build a custom addClientAuthentication function

Since createPrivateKeyJwtAuth already supports a claims parameter internally, this change simply threads it through PrivateKeyJwtProviderOptions — minimal surface area change with significant usability improvement.

Changes

• packages/client/src/client/authExtensions.ts:
  • Added optional claims?: Record<string, unknown> to PrivateKeyJwtProviderOptions
  • Pass claims through to createPrivateKeyJwtAuth in the constructor
• packages/client/test/client/authExtensions.test.ts:
  • Added test verifying custom claims appear in the signed JWT via createPrivateKeyJwtAuth
  • Added test verifying custom claims pass through PrivateKeyJwtProvider

Test plan

• All 352 client tests pass (350 existing + 2 new)
• Build passes (pnpm build:all)
• Typecheck passes (pnpm typecheck:all)
• Lint + Prettier pass (pnpm lint:all)
• Lefthook pre-push hooks pass

AI Disclosure

AI assistance (Claude) was used for issue research. The implementation was written and reviewed by the author.

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