Create Azure ADB2C Tenant broken

Hi,

When I run the sample body for creating an ADB2C tenant at https://github.com/Azure/azure-rest-api-specs/blob/0466e8633f08fa752525244d1d0fc29fd791d076/specification/cpim/resource-manager/Microsoft.AzureActiveDirectory/stable/2021-04-01/examples/createTenant.json, I get back a 202 pointing me to a long running operation, but that operation fails with a 400 error and the message
`"The domain suffix specified '' and correct value is 'onmicrosoft.com'."`

I imagine this is a problem with something deeper in azure, where this endpoint doesn't work, but I'm not sure where to log that bug.

Start with specification/cpim/resource-manager/Microsoft.AzureActiveDirectory/stable/2021-04-01/examples/createTenant.json and run its sample request. Trace the 202 response to the long-running operation and compare the resulting 400 error with the specification. Done means determining whether the example/specification is wrong or the Azure service must be contacted, then recording the evidence and next action.

Written by the indexing model from the issue text.