### 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
INTERNAL_AWS_ACCESS_KEY_ID = "__internal_call__"
INTERNAL_AWS_SECRET_ACCESS_KEY = "__internal_call__"
LS_LOG_TRACE = "trace"
LS_LOG_TRACE_INTERNAL = "trace-internal"
TRACE_LOG_LEVELS = [LS_LOG_TRACE, LS_LOG_TRACE_INTERNAL]
OFFICIAL_IMAGES = [
    "localstack/localstack",
    "localstack/localstack-light",
    "localstack/localstack-full",
]
S3_VIRTUAL_HOSTNAME = "s3.%s" % LOCALHOST_HOSTNAME
S3_STATIC_WEBSITE_HOSTNAME = "s3-website.%s" % LOCALHOST_HOSTNAME
DEFAULT_DEVELOP_PORT = 5678
DEFAULT_BUCKET_MARKER_LOCAL = "__local__"
OS_USER_OPENSEARCH = "localstack"
READY_MARKER_OUTPUT = "Ready."
MOTO_ACCOUNT_ID = TEST_AWS_ACCOUNT_ID
def patch_moto_account_id():
    
    try:
        from moto import core as moto_core
        from moto.core import models as moto_core_models
        moto_core.ACCOUNT_ID = moto_core_models.ACCOUNT_ID = MOTO_ACCOUNT_ID
    except Exception:
        
        pass
if not os.environ.get("SKIP_PATCH_MOTO_ACCOUNT_ID"):
    
    patch_moto_account_id()