Replace DefaultAzureCredential

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"DefaultAzureCredential is undoubtedly the easiest way to get started with the Azure Identity client library, but with that convenience comes tradeoffs. Once you deploy your app to Azure, you should understand the app's authentication requirements. For that reason, strongly consider moving from DefaultAzureCredential to one of the following solutions:

A specific credential implementation, such as ManagedIdentityCredential.
A pared-down ChainedTokenCredential implementation optimized for the Azure environment in which your app runs".

https://learn.microsoft.com/en-us/azure/developer/python/sdk/authentication/credential-chains?tabs=dac#usage-guidance-for-defaultazurecredential

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Done:
Azure/gpt-rag-agentic#16
Azure/gpt-rag-orchestrator#113
Azure/gpt-rag-ingestion#118
Azure/gpt-rag-frontend#53