[Discuss] Use sidekiq instead of delayed job

Not for merging!
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Wanted to discuss the idea of using sidekiq instead of delayed_job and to move the slow parts of the update user action into the background

* Added a worker for UpdateUserPermission, so that the update action
does not time out
* Moved existing worker to app/workers
* Modified the return paths of update user to the index
* Removed rescues in the propigator so that exception emails are sent

TODO
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* update the tests
* deployment