[Extensions] Fixing managed identity error text

[jsquire]

Summary

The focus of these changes is to improve the error messaging when configuration provided for one of the managed identity credentials is incorrect.

[Copilot]

Pull Request Overview

This PR improves error messaging for managed identity credential configuration issues. The changes clarify what configuration values must be provided and correct inconsistencies in the error messages.

Key Changes:

• Updated error messages to remove references to environment variables (configuration only)
• Fixed inconsistent identifier names in error messages to match actual configuration keys
• Corrected the order of valid identifiers based on whether federated identity is being used

[scottaddie]

This logic was correct before. If federated, clientId is required. The underlying ClientAssertionCredential will need it.

Suggested change

	? "'managedIdentityClientId', 'managedIdentityResourceId', or 'managedIdentityObjectId'"
	: "'clientId', 'managedIdentityClientId', 'managedIdentityResourceId', or 'managedIdentityObjectId'";
	? "'clientId', 'managedIdentityClientId', 'managedIdentityResourceId', or 'managedIdentityObjectId'"
	: "'managedIdentityClientId', 'managedIdentityResourceId', or 'managedIdentityObjectId'";

[jsquire]

You're missing L426. The message ends up being:

Managed Identity (non-fed)
I need a 'clientId', 'managedIdentityClientId', 'managedIdentityResourceId', or 'managedIdentityObjectId' to use.

Federated Managed Identity

I need a clientId AND "'managedIdentityClientId', 'managedIdentityResourceId', or 'managedIdentityObjectId' to use.