### 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
return validator["validateRequestBody"]
    @staticmethod
    def should_validate_request(validator):
        return validator.get("validateRequestParameters")
def run_authorizer(invocation_context: ApiInvocationContext, authorizer: Dict):
    
    pass
def authorize_invocation(invocation_context: ApiInvocationContext):
    client = aws_stack.connect_to_service("apigateway")
    authorizers = client.get_authorizers(restApiId=invocation_context.api_id, limit=100).get(
        "items", []
    )
    for authorizer in authorizers:
        run_authorizer(invocation_context, authorizer)
def validate_api_key(api_key: str, stage: str):
    usage_plan_ids = []
    client = aws_stack.connect_to_service("apigateway")
    usage_plans = client.get_usage_plans()
    for item in usage_plans.get("items", []):
        api_stages = item.get("apiStages", [])
        for api_stage in api_stages:
            if api_stage.get("stage") == stage:
                usage_plan_ids.append(item.get("id"))
    for usage_plan_id in usage_plan_ids:
        usage_plan_keys = client.get_usage_plan_keys(usagePlanId=usage_plan_id)
        for key in usage_plan_keys.get("items", []):
            if key.get("value") == api_key:
                return True
    return False
def is_api_key_valid(is_api_key_required: bool, headers: Dict[str, str], stage: str):