feat(azure)!: use managed identity to access object storage

[modridi]

Description of the changes

User can now choose between key-based and identity-based access to object storage.
The variable metrics_storage is refactored as follow:

metrics_storage = {
  container       = azurerm_storage_container.metrics.name
  storage_account = azurerm_storage_account.metrics.name

  managed_identity_node_rg_name = module.cluster.node_resource_group # Unset when using account key.

  storage_account_key = azurerm_storage_account.metrics.primary_access_key # Unset when using a managed identity
}

Imporant: when using identity-based access, aad-pod-identity must be declared as module dependency.

Breaking change

• No
• Yes (in the Helm chart(s))
• Yes (in the module itself): see new variable for setting storage parameters above.

Tests executed on which distribution(s)

• KinD
• AKS (Azure)
• EKS (AWS)
• Scaleway
• SKS (Exoscale)