Revert "Revert "Remove action mailer dependency""

[erkde]

The deploy script (private repo) for smart answers and the frontend app is now updated to remove the deploy task that copied the file mailer.rb, containing GDS mailer config, into the config/initializers as a post deploy task.

Reverts #2357, which reverted the original PR /pull/2348 to remove action_mailer from smart answers.

[chrisroos]

Can you update the description to explain why we're able to merge this again? Presumably the thing that initially caused problems in #2357 has now been fixed/removed?

[erkde]

thanks @chrisroos - have updated the description

[chrisroos]

Thanks for updating the description, @erikse.

Are we confident that deploying this won't cause any problems now that the related initializer has been removed? If we're unsure, is there any way of boosting confidence before we merge/deploy?

I'm happy for this to be merged if/when we're confident it's not going to cause any problems after deploying.

[erkde]

Yeah, last time we saw an error in Errbit when it was deployed to integration by CI so I'd imagine we would see that again if for some reason the PR @mattbostock merged has been reverted, or missed updating the smart answers script.