[Azure OpenAI] Migrate to Entra ID authentication, for improved security

[jdubois]

We currently use API Keys to connect to Azure OpenAI, which isn't the best option for security.

Here's a detailed explanation https://techcommunity.microsoft.com/t5/microsoft-developer-community/using-keyless-authentication-with-azure-openai/ba-p/4111521 from my colleague @pamelafox

This PR:

• Updates the current script for deploying the models:
  • It adds a random number to the resource group name, so we have less naming collisions
  • It uses a new preview feature, to completely remove API Key authentication
  • It gives the role to the current user, using az cli: this is how you would normally test, and run inside GitHub Actions (authentication is now done through Azure CLI)
  • It adds a system managed identity, in the case you want to access the models from another Azure service
• Updates the test suite, so it uses this new authentication mechanism

[langchain4j]

@jdubois pardon for the delayed review, somehow this PR got lost... Could you please check the conflicts? 🙏

[jdubois]

@langchain4j conflicts fixed, but please have a look at this 2 comments:

• The project name (line 8) uses a $RANDOM name, so we don't have conflicts when deploying the models (otherwise only one person in the world can deploy this)
• davinci-002 isn't available in eastus so this one won't deploy -> I don't think you use it, so how about deleting it?