### 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
"ingest-attachment",
    "analysis-kuromoji",
    "mapper-murmur3",
    "mapper-size",
    "analysis-phonetic",
    "analysis-smartcn",
    "analysis-stempel",
    "analysis-ukrainian",
]
ELASTICSEARCH_DELETE_MODULES = ["ingest-geoip"]
OPENSEARCH_DEFAULT_VERSION = "OpenSearch_1.1"
ELASTICMQ_JAR_URL = (
    "https://s3-eu-west-1.amazonaws.com/softwaremill-public/elasticmq-server-1.1.0.jar"
)
STS_JAR_URL = "https://repo1.maven.org/maven2/com/amazonaws/aws-java-sdk-sts/1.11.14/aws-java-sdk-sts-1.11.14.jar"
STEPFUNCTIONS_ZIP_URL = "https://s3.amazonaws.com/stepfunctionslocal/StepFunctionsLocal.zip"
KMS_URL_PATTERN = "https://s3-eu-west-2.amazonaws.com/local-kms/3/local-kms_<arch>.bin"
DYNAMODB_JAR_URL = "https://s3-us-west-2.amazonaws.com/dynamodb-local/dynamodb_local_latest.zip"
API_ENDPOINT = os.environ.get("API_ENDPOINT") or "https://api.localstack.cloud/v1"
ANALYTICS_API = os.environ.get("ANALYTICS_API") or "https://analytics.localstack.cloud/v0"
LOCALSTACK_WEB_PROCESS = "LOCALSTACK_WEB_PROCESS"
LOCALSTACK_INFRA_PROCESS = "LOCALSTACK_INFRA_PROCESS"
AWS_REGION_US_EAST_1 = "us-east-1"
DEFAULT_LAMBDA_CONTAINER_REGISTRY = "lambci/lambda"
try:
    MAX_POOL_CONNECTIONS = int(os.environ["MAX_POOL_CONNECTIONS"])
except Exception:
    MAX_POOL_CONNECTIONS = 150
TEST_AWS_ACCESS_KEY_ID = "test"
TEST_AWS_SECRET_ACCESS_KEY = "test"