Deal with string/int conversion when validating variables

```
contacts:
url: ${api_url}/contacts/
validation:
status: 200
json:
# contacts are listed in reverse order or creation
1:
user: ${alice data.id}
```

The db field is an integer while the resolved variable substitution comes in as a string, leading to a failure:

```
❌ contacts FAILED : json invalid: index '1' validation error: key 'user' validation error: (2) is not equal to ("2")
```