Milestone M27 update

Replaced instances of Sidekiq::Testing.fake! with Sidekiq::Testing.inline! across the tests

Refactors across the codebase against earlier done Ruby best practices and Rails best practices audit was done.

A bug was identified during hiring assessments where exception handling for custom slugs across two quizzes not being unique was not handled. We shipped a fix for it.

Notification emails related to new submission were failing to get delivered with an error if the questions/options contained images. This was identified while testing. A fix was shipped for this issue.