It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
Rails 6.1.3.1 deprecates a few API and has some internal changes that break our tests suite, so this commit fixes all the deprecations and errors and now Discourse should be fully compatible with Rails 6.1.3.1. We also have a new release of the rails_failover gem that's compatible with Rails 6.1.3.1.
This adds a new table UserNotificationSchedules which stores monday-friday start and ends times that each user would like to receive notifications (with a Boolean enabled to remove the use of the schedule). There is then a background job that runs every day and creates do_not_disturb_timings for each user with an enabled notification schedule. The job schedules timings 2 days in advance. The job is designed so that it can be run at any point in time, and it will not create duplicate records.
When a users saves their notification schedule, the schedule processing service will run and schedule do_not_disturb_timings. If the user should be in DND due to their schedule, the user will immediately be put in DND (message bus publishes this state).
The UI for a user's notification schedule is in user -> preferences -> notifications. By default every day is 8am - 5pm when first enabled.
