fix: Modified the code for default azure credential

[Prajwal-Microsoft]

Purpose

• ...
  This pull request refactors how Azure credentials are instantiated throughout the codebase. The main change is to create a single instance of DefaultAzureCredential and reuse it when initializing Azure SDK clients, rather than creating a new credential inline for each client. This makes the code more efficient and consistent.

Credential initialization refactor:

• All occurrences of inline new DefaultAzureCredential(DefaultAzureCredential.DefaultEnvironmentVariableName) in client constructors are replaced by first creating a DefaultAzureCredential instance and then passing it to the client. This affects:
  • AzureStorageQueueService (AzureStorageQueueService.cs)
  • BlobServiceClient in StorageAccessUtil (StorageAccessUtil.cs)
  • DocumentAnalysisClient in AzureAIDocIntelEngine (AzureAIDocIntelEngine.cs)
  • SearchIndexClient in AzureAISearchMemory (AzureAISearchMemory.cs)
  • BlobServiceClient in AzureBlobsStorage (AzureBlobsStorage.cs)
  • AzureOpenAITextEmbeddingGenerationService in AzureOpenAITextEmbeddingGenerator (AzureOpenAITextEmbeddingGenerator.cs)
  • OpenAIClient in AzureOpenAITextGenerator (AzureOpenAITextGenerator.cs)
  • QueueClient in AzureQueuesPipeline (AzureQueuesPipeline.cs)

This change improves code readability, reduces duplication, and may help with credential caching and performance.

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

Verify that the following are valid

• ...

Other Information