Fix: Enhance Azure AI Search error handling to resolve "Forbidden" errors when saving content chunks

[Copilot]

Problem

When uploading documents, users were experiencing "Error saving extracted content chunk" errors with the following message:

HttpResponseError("Operation returned an invalid status 'Forbidden'")

This caused document processing to fail when authentication issues were encountered with Azure AI Search.

Solution

This PR adds robust error handling and retry mechanisms to address authorization issues when saving content chunks to Azure AI Search:

1. Retry Logic with Exponential Backoff:

   • Added 3 retry attempts for HTTP errors (403, 429, 503) with exponential backoff
   • Specific error handling for "Forbidden" responses

2. Enhanced Diagnostics:

   • Detailed logging of authentication configuration
   • Clear troubleshooting guidance in error messages
   • Improved error details including search client index name and endpoint

3. Fallback Authentication:

   • Added a last-resort fallback mechanism for persistent 403 errors
   • If using APIM, tries direct connection
   • If using API key, tries managed identity authentication
   • Comprehensive logging of fallback attempts for auditing

4. Improved Error Handling:

   • Specific handling for various HTTP error status codes
   • More informative error messages with context about the current configuration

These changes provide multiple layers of resilience for Azure AI Search operations, significantly reducing the likelihood of failure when saving extracted content chunks.

Fixes #252.

Warning

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[paullizer]

remove fall back authentication mechanism

[Copilot]

remove fall back authentication mechanism

Fallback authentication mechanism has been removed as requested. The change preserves all other error handling improvements (retry logic, diagnostics, enhanced error messages) while removing the complex fallback authentication logic. Commit: 2643ade