Document DefaultAzureCredential breaking change in client integrations

[Copilot]

• Analyze all files referencing DefaultAzureCredential across the docs
• Review PR Refactor DefaultAzureCredential usage dotnet/aspire#14951 to understand the new credential behavior
• Create a new common Azure doc page (azure-default-credential.mdx) explaining the default credential behavior
• Add a breaking change section in aspire-13-2.mdx for the credential change
• Update client integration docs that say "the DefaultAzureCredential is used" to point to the new common doc
  • azure-storage-blobs-client.mdx
  • azure-storage-queues-client.mdx
  • azure-event-hubs-client.mdx
  • azure-ai-inference-client.mdx
  • azure-app-configuration-client.mdx
  • azure-ai-search-client.mdx
  • azure-openai-client.mdx
  • azure-web-pubsub-client.mdx
  • azure-storage-datalake.mdx
  • azure-postgresql-client.mdx (in efcore/azure-postgresql)
• Add sidebar entry for the new doc page
• Verify changes render correctly with the dev server

Original prompt

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This section details on the original issue you should resolve

<issue_title>[13.2] Document breaking change on DefaultAzureCredential in client integrations</issue_title>
<issue_description>See dotnet/aspire#14951 for more information.

Using the parameterless ctor of DefaultAzureCredential is not recommended. Instead try to detect when we are running in Azure and use Azure credentials. Fallback to using just development credentials when we can't detect we are in Azure.

See https://learn.microsoft.com/dotnet/azure/sdk/authentication/credential-chains?tabs=dac#usage-guidance-for-defaultazurecredential for more information.

Users can always provide their own to override this behavior.

This is a breaking change for anyone depending on credentials other than ManagedIdentity working in an Azure service.

If another credential is necessary in your application, you can use the following code:

builder.AddAzureBlobServiceClient(
    "blobs",
    settings =>
    {
        settings.Credential = new EnvironmentCredential();
    });

We should also update any documents in Azure that say

If no credential is configured, the DefaultAzureCredential is used

Instead it should say

If no credential is configured, a default credential is used. See [link to common Azure docs] for more information.</issue_description>

<agent_instructions>Add docs for:

• What's new in a breaking change
• In a common Azure document, explain the default credential that is used based on Refactor DefaultAzureCredential usage dotnet/aspire#14951
• Update all the docs that say the DefaultAzureCrential is used and instead point them to the new doc</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [13.2] Document breaking change on DefaultAzureCredential in client integrations #516

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