### 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
if "requestModels" not in resource or not resource["requestModels"]:
            return False
        schema_name = resource["requestModels"].get(APPLICATION_JSON)
        model = self.apigateway_client.get_model(
            restApiId=self.context.api_id,
            modelName=schema_name,
        )
        if not model:
            return False
        try:
            validate(instance=json.loads(self.context.data), schema=json.loads(model["schema"]))
            return True
        except ValidationError as e:
            LOG.warning("failed to validate request body", e)
            return False
    
    def validate_parameters_and_headers(self, resource):
        return True
    @staticmethod
    def should_validate_body(validator):