### 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
cfn = connect_to_service("cloudformation")
    cfn.create_stack(StackName=stack_name, TemplateBody=template_body)
    
    return await_stack_completion(stack_name)
def await_stack_status(stack_name, expected_statuses, retries=20, sleep=2, region_name=None):
    def check_stack():
        stack = get_stack_details(stack_name, region_name=region_name)
        if stack["StackStatus"] not in expected_statuses:
            raise Exception(
                'Status "%s" for stack "%s" not in expected list: %s'
                % (stack["StackStatus"], stack_name, expected_statuses)
            )
        return stack
    expected_statuses = (
        expected_statuses if isinstance(expected_statuses, list) else [expected_statuses]
    )
    return retry(check_stack, retries, sleep)
def await_stack_completion(stack_name, retries=20, sleep=2, statuses=None, region_name=None):
    statuses = statuses or ["CREATE_COMPLETE", "UPDATE_COMPLETE", "DELETE_COMPLETE"]
    return await_stack_status(
        stack_name, statuses, retries=retries, sleep=sleep, region_name=region_name
    )
def get_ecr_repository_arn(name, account_id=None, region_name=None):
    pattern = "arn:aws:ecr:%s:%s:repository/%s"
    return _resource_arn(name, pattern, account_id=account_id, region_name=region_name)