### 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
return to_str(search_str) in path or to_bytes(search_str) in data_bytes
    if path == "/" and b"QueueName=" in data_bytes:
        return "sqs", config.service_port("sqs")
    if "Action=ConfirmSubscription" in path:
        return "sns", config.service_port("sns")
    if path.startswith("/2015-03-31/functions/"):
        return "lambda", config.service_port("lambda")
    if _in_path_or_payload("Action=AssumeRoleWithWebIdentity"):
        return "sts", config.service_port("sts")
    if _in_path_or_payload("Action=AssumeRoleWithSAML"):
        return "sts", config.service_port("sts")
    if _in_path_or_payload("Action=AssumeRole"):
        return "sts", config.service_port("sts")
    
    if _in_path_or_payload("QueueUrl=") and _in_path_or_payload("Action="):
        return "sqs", config.service_port("sqs")
    if matches_service_action("sqs", action, version=version):
        return "sqs", config.service_port("sqs")
    
    if matches_service_action("sns", action, version=version):
        return "sns", config.service_port("sns")
    
    stripped = path.strip("/")
    if method in ["GET", "HEAD"] and stripped:
        
        return "s3", config.service_port("s3")
    
    if stripped and "/" not in stripped: