### 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
self,
        method: str,
        path: str,
        data: MessagePayload,
        headers: Headers,
        response: Response,
    ) -> Optional[RoutingResponse]:
        """Return a RoutingResponse with modified response data, or None to forward the response
        unmodified"""
        return None
class ArnPartitionRewriteListener(MessageModifyingProxyListener):
    """
    Intercepts requests and responses and tries to adjust the partitions in ARNs within the
    intercepted requests.
    For incoming requests, the default partition is set ("aws").
    For outgoing responses, the partition is adjusted based on the region in the ARN, or by the
    default region
    if the ARN does not contain a region.
    This listener is used to support other partitions than the default "aws" partition (f.e.
    aws-us-gov) without
    rewriting all the cases where the ARN is parsed or constructed within LocalStack or moto.
    In other words, this listener makes sure that internally the ARNs are always in the partition
    "aws", while the
    client gets ARNs with the proper partition.
    """
    
    DEFAULT_INBOUND_PARTITION = "aws"
    class InvalidRegionException(Exception):