Add default to authorized_keys_enabled setting

Reminder: The original migration was fixed retroactively a few commits ago, so people who did not ever run GitLab 9.3.0 already have a column that defaults to true and disallows nulls. I have tested on PostgreSQL and MySQL that it is safe to run this migration regardless.

Affected customers who did run 9.3.0 are the ones who need this migration to fix the authorized_keys_enabled column.

The reason for the retroactive fix plus this migration is that it allows us to run a migration in between to fix the authorized_keys file only for those who ran 9.3.0.

db/migrate/20170627211700_add_default_to_authorized_keys_enabled_application_setting.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddDefaultToAuthorizedKeysEnabledApplicationSetting < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    change_column :application_settings, :authorized_keys_enabled, :boolean, default: true
+    change_column_null :application_settings, :authorized_keys_enabled, false, true
+  end
+
+  def down
+    change_column_null :application_settings, :authorized_keys_enabled, true
+    change_column :application_settings, :authorized_keys_enabled, :boolean, default: nil
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170626202753) do
+ActiveRecord::Schema.define(version: 20170627211700) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -141,7 +141,7 @@ ActiveRecord::Schema.define(version: 20170626202753) do
     t.integer "mirror_max_delay", default: 5, null: false
     t.integer "mirror_max_capacity", default: 100, null: false
     t.integer "mirror_capacity_threshold", default: 50, null: false
-    t.boolean "authorized_keys_enabled"
+    t.boolean "authorized_keys_enabled", default: true, null: false
     t.boolean "help_page_hide_commercial_content", default: false
     t.string "help_page_support_url"
   end