Make validation error raising optional

[dfulu]

We have a few forecast validation functions which do some sanity checking on the forecast. For example the functions here.

These functions will crash the forecast if something goes wrong. This means that we will not log these bad forecasts to our database and we will not record them. This makes it harder for us to analyse what went wrong and to try to improve our forecast.

The app also has the option to run multiple forecast models simultaneously. These validation will crash the app and log no forecasts, if a single one of these models produces a bad forecast. Again, this is bad.

We should

• Make the validation functions optional so that we can collect the bad forecast results in our dev environment
• Change the way we use the validation functions so that one model producing a bad forecast will not stop all models from logging their forecasts

[utsav-pal]

please check it