The filter option in the recipe needs more testing and tweaking

For example, the following config in the recipe:
```
<filter>
  date_in = >= 2020-01-01
</filter>
```
The result for `$where` is:
```
{ date_in => ">= 2020-01-01" }
```
but it should be:
```
{ date_in => { '>=', '2020-01-01' } }
```