Document Azure service principal auth in snapshot/agent.mdx (#21942)

* Update agent.mdx

Starting from Consul v1.20.1+ent, Consul supports using Azure Blob Storage for the snapshot agent via Azure Service Principal  ID and Secret authentication. I've successfully tested this configuration in my lab environment and have added the relevant parameters to this documentation for completeness.

* Update website/content/commands/snapshot/agent.mdx

Co-authored-by: Blake Covarrubias <[email protected]>

* Update website/content/commands/snapshot/agent.mdx

Co-authored-by: Blake Covarrubias <[email protected]>

* Update website/content/commands/snapshot/agent.mdx

Co-authored-by: Blake Covarrubias <[email protected]>

* Update website/content/commands/snapshot/agent.mdx

Co-authored-by: Blake Covarrubias <[email protected]>

---------

Co-authored-by: Blake Covarrubias <[email protected]>

Author: SuyashHashiCorp

website/content/commands/snapshot/agent.mdx

@@ -396,9 +396,16 @@ These options cannot be used when using `backup_destinations` in a config file.
 - `-azure-blob-container-name` - Container to use. Required for Azure blob storage, and setting this
   disables local storage.
 
-* `-azure-blob-environment` - Environment to use. Defaults to AZUREPUBLICCLOUD. Other valid environments
+- `-azure-blob-environment` - Environment to use. Defaults to AZUREPUBLICCLOUD. Other valid environments
   are AZURECHINACLOUD, AZUREGERMANCLOUD and AZUREUSGOVERNMENTCLOUD. Introduced in Consul 1.7.3.
 
+~> The following options were introduced in v1.20.1+ent.
+
+- `-azure-blob-service-principal-id` - The ID of the service principal that owns the blob object.
+- `-azure-blob-service-principal-secret` - The secret of the service principal that owns the blob object.
+
+- `-azure-blob-tenant-id` - The ID of the tenant that owns the Azure blob.
+
 #### Google Cloud Storage options
 
 ~> This option is deprecated when used with a top-level `google_storage` object in a config file. Use `snapshot_agent -> backup_destinations -> google_storage[0]` in a config file instead.