Add pubsub connection

[esloho]

Closes https://github.com/CartoDB/global_metrics/issues/31

As done in https://github.com/CartoDB/cartodb-central/pull/2598, this PR introduces the same PubSubTracker for sending events to PubSub from cartodb. Since in this case we must cover different authentication scenarios (like a future on-premise case), tracker initialization in this implementation includes additional cases.

The idea is to later remove the Segments events so only PubSub ones are sent, thus the duplication of the event models.

[gonzaloriestra]

Nice! 👏 I've added a few minor comments.

We must remember to carefully test Instagram, Dropbox and Google integrations.

[esloho]

After experiencing some problems with the async publishing of pubsub events in central we decided to try a different approach and replace it by sync publishing through resque jobs. Once we check that approach is working I'll perform the same change in this PR :)

[gonzaloriestra]

👌

[gonzaloriestra]

✔️ Acceptance OK

Tested with several events that they are logged and also received in Pub/Sub.

[esloho]

After reviewing the full list of events and do some cleaning, these are the ones that should be published to pubsub at the moment:

• map_created
• map_deleted
• map_exported
• map_published
• map_exported
• dataset_created
• dataset_deleted
• analysis_created
• anañysis_updated
• analysis_deleted
• oauth_app_created
• oauth_app_deleted
• oauth_app_user_created
• oauth_app_user_deleted
• quota_exceeded

Acceptance: These should appear in Rollbar as info messages and in the corresponding project in Google Cloud every time the action is performed by the user.

/cc @gonzaloriestra

[esloho]

Blocked until the necessary credentials for pubsub are created in production.