🔒 Replace hardcoded secrets in docstrings with placeholders

[shivan4030]

🎯 What: Replace dummy client credential values in AuthCredential docstring examples with secure descriptive placeholders.

⚠️ Risk: Hardcoded fake secret strings like "secret" can be incorrectly flagged by automated security scanners, creating false positives that require manual triage and reduce signal-to-noise ratio in vulnerability reports.

🛡️ Solution: Replaced "secret" and "1234" in example docstrings with explicit placeholders like YOUR_CLIENT_SECRET and YOUR_CLIENT_ID to comply with secure documentation practices.

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PR created automatically by Jules for task 5801770483287956393 started by @shivan4030

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