### 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
def __init__(self, region=None, prefix=None):
        
        
        self.region = region or get_local_region()
        
        self.prefix = prefix
    def apply_json(self, j):
        if isinstance(j, str):
            j = json.loads(j)
        self.__dict__.update(j)
    @staticmethod
    def from_string(s):
        parts = s.split(":")
        if len(parts) == 1:
            if s in PREDEFINED_ENVIRONMENTS:
                return PREDEFINED_ENVIRONMENTS[s]
            parts = [get_local_region(), s]
        if len(parts) > 2:
            raise Exception('Invalid environment string "%s"' % s)
        region = parts[0]
        prefix = parts[1]
        return Environment(region=region, prefix=prefix)
    @staticmethod
    def from_json(j):
        if not isinstance(j, dict):
            j = j.to_dict()
        result = Environment()
        result.apply_json(j)
        return result
    def __str__(self):