### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Currently the VTL template for `request_templates` is not processed properly:

```
#set( $body = $input.json("$") )

#macro( loop $map )
{
    #foreach($key in $map.keySet())
        #set( $k = $util.escapeJavaScript($key) )
        #set( $v = $util.escapeJavaScript($map.get($key)).replaceAll("\\'", "'") )
        "$k": "$v"
        #if( $foreach.hasNext ) , #end
    #end
}
#end

{
    "enhancedAuthContext": #loop($context.authorizer),

    "headers": #loop($input.params().header),

    "query": #loop($input.params().querystring),

    "path": #loop($input.params().path),

    "identity": #loop($context.identity),

    "stageVariables": #loop($stageVariables),
}
EOF
}
```

results in,

```
'

{
    "enhancedAuthContext": {
    }
,

    "headers": {
    }
,

    "query": {
    }
,

    "path": {
    }
,

    "identity": {
    }
,

    "stageVariables": {
    }
,
}
'
```

### Expected Behavior

The template should be rendered and have the JSON properties.

### How are you starting LocalStack?

Custom (please describe below)

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    awslocal s3 mb s3://mybucket


### Environment

```markdown
- OS: MacOS
- LocalStack: 0.14
```


### Anything else?

This example can be used to validate.
https://github.com/localstack/localstack-terraform-samples/tree/master/apigateway-lambda-velocity
if not is_api_key_required:
        return True
    api_key = headers.get("X-API-Key")
    if not api_key:
        return False
    return validate_api_key(api_key, stage)
def update_content_length(response: Response):
    if response and response.content is not None:
        response.headers["Content-Length"] = str(len(response.content))
def apply_request_parameters(
    uri: str, integration: Dict[str, Any], path_params: Dict[str, str], query_params: Dict[str, str]
):
    request_parameters = integration.get("requestParameters")
    uri = uri or integration.get("uri") or integration.get("integrationUri") or ""
    if request_parameters:
        for key in path_params:
            
            request_param_key = f"integration.request.path.{key}"
            request_param_value = f"method.request.path.{key}"
            if request_parameters.get(request_param_key, None) == request_param_value:
                uri = uri.replace(f"{{{key}}}", path_params[key])
    if integration.get("type") != "HTTP_PROXY" and request_parameters:
        for key in query_params.copy():
            request_query_key = f"integration.request.querystring.{key}"
            request_param_val = f"method.request.querystring.{key}"
            if request_parameters.get(request_query_key, None) != request_param_val:
                query_params.pop(key)
    return add_query_params_to_url(uri, query_params)
def apply_response_parameters(invocation_context: ApiInvocationContext):