DEV: Catch exception in operation handler

Now it's difficult to debug issues if backend fails with exception (e.g. KeyError):

```
@sdk.operation(..)
def operation(_, request):
    key = request['resource']['userType']
    ...
```


If we don't pass userType - the code fails, and Aidbox returns 500 without details.

Let's add some useful information for DEV environment (stack trace + error message)



