fix: Fix provided for using Default Azure credentials based on environment

[Prajwal-Microsoft]

Purpose

This pull request updates Azure authentication across multiple services and components to use DefaultAzureCredential instead of ManagedIdentityCredential, and standardizes the environment variable configuration for Azure credentials. It also upgrades the Azure.Identity NuGet package to version 1.16.0 throughout the solution. These changes improve flexibility and compatibility with different Azure authentication scenarios.

Authentication Modernization:

• Replaced all usages of ManagedIdentityCredential with DefaultAzureCredential(DefaultAzureCredential.DefaultEnvironmentVariableName) in service constructors and client builders, including BlobServiceClient, QueueClient, DocumentAnalysisClient, SearchIndexClient, OpenAIClient, and other Azure SDK clients. This enables support for multiple authentication mechanisms and better local development experience. [1] [2] [3] [4] [5] [6] [7] [8]

Dependency Upgrades:

• Upgraded the Azure.Identity NuGet package from versions 1.12.0/1.13.2 to 1.16.0 in all affected .csproj files for host, storage, web client, and kernel memory extensions. [1] [2] [3] [4] [5] [6] [7] [8] [9]

Environment Variable Standardization:

• Added or updated the AZURE_TOKEN_CREDENTIALS environment variable to ManagedIdentityCredential in relevant Dockerfiles and set it to dev for local development in Program.cs. This ensures consistent credential selection across environments. [1] [2] [3]

These updates collectively improve Azure authentication reliability, developer experience, and maintainability across the codebase.

Does this introduce a breaking change?

• Yes
• No

Golden Path Validation

• I have tested the primary workflows (the "golden path") to ensure they function correctly without errors.

Deployment Validation

• I have validated the deployment process successfully and all services are running as expected with this change.

What to Check

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