The equivalence of launch_block_device_mappings(aws) but for azure - amazon-web-services

Question

I am using packer to build ami. I have the AWS one as follows:
{
"name": "ami",
"type": "amazon-ebs",
"region": "us-west-1",
"access_key": "{{user `aws_access_key`}}",
"secret_key": "{{user `aws_secret_key`}}",
"ami_users": "{{user `ami_account_ids`}}",
"ami_regions": "{{user `ami_regions`}}",
"source_ami": "{{user `source_ami`}}",
"instance_type": "t2.2xlarge",
"ssh_username": "ubuntu",
"ami_name": "{{user `tag`}}-{{timestamp}}",
"shutdown_behavior": "stop",
"launch_block_device_mappings": [
{
"device_name": "/dev/sda1",
"volume_size": 30,
"volume_type": "gp2",
"delete_on_termination": true
},
{
"device_name": "/dev/sdb",
"volume_size": 50,
"volume_type": "gp2",
"delete_on_termination": true
},
{
"device_name": "/dev/sdc",
"volume_size": 30,
"volume_type": "gp2",
"delete_on_termination": true
}
]
}
I am trying to recreate the above specification but for azure and am stuck on the disk/block device part. I am trying to find the equivalence of launch_block_device_mappings but for azure. The current code of azure is as follows:
{
"name": "azure",
"type": "azure-arm",
"client_id": "{{user `azure_client_id`}}",
"client_secret": "{{user `azure_client_secret`}}",
"tenant_id": "{{user `azure_tenant_id`}}",
"subscription_id": "{{user `azure_subscription_id`}}",
"managed_image_resource_group_name": "images",
"managed_image_name": "{{user `tag`}}-{{timestamp}}",
"ssh_username": "ubuntu",
"ssh_private_key_file": "~/.ssh/id_rsa",
"os_type": "Linux",
"os_disk_size_gb": 30,
"disk_additional_size": [50, 30],
"image_publisher": "Canonical",
"image_offer": "UbuntuServer",
"image_sku": "18.04-LTS",
"location": "{{user `azure_region`}}",
"vm_size": "Standard_D4s_v3"
}