SDK - Support MSI authentication in Azure Container App and App Service like environments

[vermacodes]

Fixes #1054

Pull Request: Enhanced Support for Azure App Service Like Environments

This pull request updates managed_identity_authorizer.go to improve support for Azure App Service like environments. Key changes include:

• Environment Check: Now checks for MSI_ENDPOINT and MSI_SECRET environment variables to detect App Service like environments.
• MSI Endpoint Update: Uses MSI_ENDPOINT as the default instead of the well-known endpoint.
• API Version Change: Switches to the 2019-08-01 API version, which requires the IDENTITY_HEADER in the HTTP request.
• Endpoint Override: Users can still override the default endpoint if needed.

These changes ensure better compatibility with Azure's managed identity in App Service like environments.

[hashicorp-cla-app]

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[hashicorp-cla-app]

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[hen-den]

This is awesome for the last months we had to use a proxy to rewrite the endpoint versions. Great work.

[vermacodes]

Thank you for your submission! We require that all contributors sign our Contributor License Agreement ("CLA") before we can accept the contribution. Read and sign the agreement

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Have you signed the CLA already but the status is still pending? Recheck it.

This has been signed, not sure why its not updating.

[kabal2010]

@vermacodes
Nice one. Will really love this pushed to production as this has been a blocker running Terraform on Azure Container Apps when authenticating with Managed Identity