Integrations - OAuth2 client credentials token cache with auto-refresh - Pull 1

[hanna-g-sn]

PR Description:

Adds a reusable Script Include that wraps RESTMessageV2 with OAuth 2.0 client-credentials support:

• Fetches and caches access tokens with an expiry buffer
• Injects Authorization: Bearer on each call
• Auto-refreshes the token once if the API returns HTTP 401
• Simple options object; works for any token endpoint and resource URL

Includes README, Script Include, and a background usage example.

Pull Request Checklist

Overview

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Code Quality

• My code is relevant to ServiceNow developers
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Repository Structure Compliance

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[ravichandra1998g]

looks good to me.