400 Bad Request- Authorization Header Missing , Azure-rm_resource

I am using the generic azure_rm_resource module to use the Azure Rest API to create CosmosDb Databases/Containers,

- name: Create CosmosDB Containers
azure_rm_resource:
state: present
resource_group: "{{resource_group}}"
method: POST
url: https://{{db_account_name}}.documents.azure.com/dbs
api_version: "2018-12-31"
subresource:
- name: example
namespace: test
body: "{{merchantContainer}}"

MerchantContainer:
{
"id": "{{containers[0]}}",
}

When debugging I see that the Authorization Header is Missing, but I am have tried logging in as Service Principal and Active Directory with the same result on both occasions.

Any help would be appreciated