Use background jobs wherever appropriate

[virajvchavan]

Possible use case:
When user logs in for the first time, currently all of his calendars with all the events are loaded all at once, and then only user is redirected to auth/:provider/callback.

If user has thousands of events, it may take a long time to load the events, and even lead to a timeout before redirecting to our website. It'll be better to start a background job and then return a success response immediately. Then just find a way to show the newly loaded events as they come. (websockets?)