### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

We are using the `Authorization` header for routing purposes

```
 "authorization: AWS4-HMAC-SHA256 <...>"
```

https://github.com/localstack/localstack/issues/5770

### Expected Behavior

Use a custom header to avoid causing confusion with backend integrations

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

Run a custom HTTP integration without authorisation

### Environment

```markdown
- OS: 
- LocalStack:
```


### Anything else?

No
if method == "PUT":
            
            return "s3", config.service_port("s3")
        if method == "POST" and is_s3_form_data(data_bytes):
            
            return "s3", config.service_port("s3")
    
    if "aws-cli/" in headers.get("User-Agent", ""):
        return "s3", config.service_port("s3")
    
    if (
        method == "POST"
        and "delete=" in path
        and b"<Delete" in data_bytes
        and b"<Key>" in data_bytes
    ):
        return "s3", config.service_port("s3")
    
    if stripped.count("/") >= 1 and method == "PUT":
        
        
        return "s3", config.service_port("s3")
    auth_header = headers.get("Authorization") or ""
    
    if auth_header.startswith("AWS "):
        return "s3", config.service_port("s3")
    
    if b"Version=2016-11-15" in data_bytes:
        return "ec2", config.service_port("ec2")
def get_service_port_for_account(service, headers):