Add null value for job tier (#34333)

Author: needuv

sdk/ml/azure-ai-ml/azure/ai/ml/constants/_job/job.py

@@ -119,15 +119,17 @@ class EntityNames:
         Basic = "basic"
         Standard = "standard"
         Premium = "premium"
-        Null = "Null"
+        Null = "null"
 
     class RestNames:
+        Null = "Null"
         Spot = "Spot"
         Basic = "Basic"
         Standard = "Standard"
         Premium = "Premium"
 
     ENTITY_TO_REST = {
+        EntityNames.Null: RestNames.Null,
         EntityNames.Spot: RestNames.Spot,
         EntityNames.Basic: RestNames.Basic,
         EntityNames.Standard: RestNames.Standard,

sdk/ml/azure-ai-ml/azure/ai/ml/entities/_job/queue_settings.py

@@ -22,7 +22,7 @@ class QueueSettings(RestTranslatableMixin, DictMixin):
     """Queue settings for a pipeline job.
 
     :ivar job_tier: Enum to determine the job tier. Possible values include: "Spot", "Basic",
-        "Standard", "Premium".
+        "Standard", "Premium", "Null".
     :vartype job_tier: str or ~azure.mgmt.machinelearningservices.models.JobTier
     :ivar priority: Controls the priority of the job on a compute.
     :vartype priority: str