feat(openIntProxyLink): Adding Openint proxy link

[pellicceama]

[!IMPORTANT] Add OpenInt proxy link feature with validation, client integration, and tests for new authentication methods.

• Feature:
  • Add openIntProxyLink in openIntProxyLink.ts for handling proxy requests with OpenInt.
  • Validate options using validateOpenIntProxyLinkOptions() for correct authentication combinations.
  • Integrate openIntProxyLink into createClient() in createClient.ts when auth options are provided.
• Tests:
  • Add tests in createClient.spec.ts for link array length and overrides.
  • Add tests in index.spec.ts for sdk-qbo to verify new authentication methods.
• Misc:
  • Update ClientOptions in createClient.ts to include auth for proxy link options.
  • Modify index.ts in sdk-qbo to support new authentication methods.
  • Add authLink.ts to handle different authentication methods.

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