Fill missing authorized projects rows

This ensures that the project_authorizations rows exist for all users
for which this data has not yet been populated.

Fixes #26194

changelogs/unreleased/fill-authorized-projects.yml

+---
+title: Fill missing authorized projects rows
+merge_request:
+author:

db/post_migrate/20170106142508_fill_authorized_projects.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class FillAuthorizedProjects < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  class User < ActiveRecord::Base
+    self.table_name = 'users'
+  end
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  # We're not inserting any data so we don't need to start a transaction.
+  disable_ddl_transaction!
+
+  def up
+    relation = User.select(:id).
+      where('authorized_projects_populated IS NOT TRUE')
+
+    relation.find_in_batches(batch_size: 1_000) do |rows|
+      args = rows.map { |row| [row.id] }
+
+      Sidekiq::Client.push_bulk('class' => 'AuthorizedProjectsWorker', 'args' => args)
+    end
+  end
+
+  def down
+  end
+end

spec/migrations/fill_authorized_projects_spec.rb

+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20170106142508_fill_authorized_projects.rb')
+
+describe FillAuthorizedProjects do
+  describe '#up' do
+    it 'schedules the jobs in batches' do
+      user1 = create(:user)
+      user2 = create(:user)
+
+      expect(Sidekiq::Client).to receive(:push_bulk).with(
+        'class' => 'AuthorizedProjectsWorker',
+        'args'  => [[user1.id], [user2.id]]
+      )
+
+      described_class.new.up
+    end
+  end
+end