[BUG] Missing Content-Length Header in BlobStorage createNamespace

### API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/efa49a123da7ce3ffe093a13832258305f529711/specification/storage/data-plane/Microsoft.BlobStorage/stable/2026-02-06/blob.json#L708

### API Spec version

2025-11-05

### Describe the bug

Azure Blobstorage Container_Create needs the header `Content-Length` set to `0`, although the body is empty. Otherwise the api will return `411 Length Required`

### Expected behavior

No error

### Actual behavior

411 Length Required

### Reproduction Steps

```
POST [{BLOB_STORAGE_URL}](https://myaccount.blob.core.windows.net)/mycontainer?restype=container
Authorization: Bearer ...
Date: Sun, 25 Sep 2011 22:50:32 GMT
x-ms-version: 2025-07-05
```

### Environment

Real BlobStorage, Azurite is generated from the spec and will accept the request without Content-Length header.

See: Azure/Azurite#2618

Start at specification/storage/data-plane/Microsoft.BlobStorage/stable/2026-02-06/blob.json around line 708 and inspect the Container_Create operation. Update the specification so an empty request includes Content-Length: 0, then verify that the generated request avoids the 411 Length Required response against real Blob Storage.

Written by the indexing model from the issue text.