After traveling back in time, it can be the case that between the call
to the service and the moment we check the current time, we moved on to
the next second.
Using Timecop.freeze takes care of that.
* Add ProMembership model
* Implement ProMembershipsController#create
* Implement basic ProMembershipsController#show
* Add ProMembership to ledger
* Populate user history after pro subscription is created
* Add fields for expiration notifications
* Add ProMemberships::ExpirationNotifier to notify users of expiring memberships
* Add tasks for recurring jobs to notify users of expiration
* Add auto_recharge column to ProMembership
* Add ProMemberships::Biller (incomplete)
* Fix specs
* Add ProMembership to Administrate
* Fix spec
* Add has_enough_credits? to User and Organization
* Add Payments::Customer class
* Finish ProMembership::Biller functionality
* Fix ProMemberships::Creator check for credits
* Disable destroy actions for ProMembershipsController
* Correctly authenticate ProMembershipsController actions
* Make sure only pro user's history can be indexed
* Add ProMembershipsController#update action for auto recharge
* Use regular AR to save new credits and add touch to the purchaser
* Clarify Pro membership create policy
* Display information about an existing pro membership
* Add UI to show page
* Add system test for Pro membership creation
* Implement edit membership
* Make sure users with pro memberships can access history and dashboard pro
* Fix padding issue
* Show a different text for a user that has credits but not enough for Pro
* Move Pro Membership functionality inside settings
* Update Pro Membership link in email notifications
* Bust all relevant caches
* Add the Pro checkmark around the website
* Use Users::ResaveArticlesJob instead of delay
* Add/remove user from pro-members chat channel
* Use the appropriate Pro checkmark
* Remove unfinished pro elements
* Remove checkmark JS
