### 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
headers["Content-Type"] = object["ContentType"]
                
                response = request_response_stream(stream=object["Body"], headers=headers)
                return response
            else:
                msg = "Request URI does not match s3 specifications"
                LOG.warning(msg)
                return make_error_response(msg, 400)
        if method == "POST":
            if uri.startswith("arn:aws:apigateway:") and ":sqs:path" in uri:
                template = integration["requestTemplates"][APPLICATION_JSON]
                account_id, queue = uri.split("/")[-2:]
                region_name = uri.split(":")[3]
                if "GetQueueUrl" in template or "CreateQueue" in template:
                    request_templates = RequestTemplates()
                    payload = request_templates.render(invocation_context)
                    new_request = f"{payload}&QueueName={queue}"
                else:
                    request_templates = RequestTemplates()
                    payload = request_templates.render(invocation_context)
                    queue_url = f"{config.get_edge_url()}/{account_id}/{queue}"
                    new_request = f"{payload}&QueueUrl={queue_url}"
                headers = aws_stack.mock_aws_request_headers(service="sqs", region_name=region_name)
                url = urljoin(config.service_url("sqs"), f"{TEST_AWS_ACCOUNT_ID}/{queue}")
                result = common.make_http_request(
                    url, method="POST", headers=headers, data=new_request
                )
                return result
            elif uri.startswith("arn:aws:apigateway:") and ":sns:path" in uri:
                invocation_context.context = get_event_request_context(invocation_context)