Enable automatic allocation of purchased storage

Instead of gating automatic allocation of additional purchased storage
for the namespace via a GL.com check, it can be gated based on a new
ApplicationSetting.

- Add column, automatic_purchased_storage_allocation, to
  application_settings table.
- Allow setting to be listed and updated via application settings API.

changelogs/unreleased/247449_auto-purchased-storage-allocation.yml

+---
+title: Enable automatic allocation of purchased storage
+merge_request: 44376
+author:
+type: changed

db/migrate/20201006014605_add_automatic_purchased_storage_allocation_to_application_settings.rb

+# frozen_string_literal: true
+
+class AddAutomaticPurchasedStorageAllocationToApplicationSettings < ActiveRecord::Migration[6.0]
+  DOWNTIME = false
+
+  def change
+    add_column :application_settings, :automatic_purchased_storage_allocation, :boolean, default: false, null: false
+  end
+end

db/schema_migrations/20201006014605

+d1a636c0b0c7f11bf5d6e882970a5286a28c3f060f89df3ac51df2e7c86f042e
\ No newline at end of file

db/structure.sql

@@ -9297,6 +9297,7 @@ CREATE TABLE application_settings (
     abuse_notification_email character varying,
     require_admin_approval_after_user_signup boolean DEFAULT false NOT NULL,
     help_page_documentation_base_url text,
+    automatic_purchased_storage_allocation boolean DEFAULT false NOT NULL,
     CONSTRAINT check_2dba05b802 CHECK ((char_length(gitpod_url) <= 255)),
     CONSTRAINT check_51700b31b5 CHECK ((char_length(default_branch_name) <= 255)),
     CONSTRAINT check_57123c9593 CHECK ((char_length(help_page_documentation_base_url) <= 255)),

doc/api/settings.md

@@ -209,6 +209,7 @@ listed in the descriptions of the relevant settings.
 | `authorized_keys_enabled`                | boolean          | no                                   | By default, we write to the `authorized_keys` file to support Git over SSH without additional configuration. GitLab can be optimized to authenticate SSH keys via the database file. Only disable this if you have configured your OpenSSH server to use the AuthorizedKeysCommand. |
 | `auto_devops_domain`                     | string           | no                                   | Specify a domain to use by default for every project's Auto Review Apps and Auto Deploy stages. |
 | `auto_devops_enabled`                    | boolean          | no                                   | Enable Auto DevOps for projects by default. It will automatically build, test, and deploy applications based on a predefined CI/CD configuration. |
+| `automatic_purchased_storage_allocation` | boolean          | no                                   | Enabling this permits automatic allocation of purchased storage within a namespace. |
 | `check_namespace_plan`                   | boolean          | no                                   | **(PREMIUM)** Enabling this will make only licensed EE features available to projects if the project namespace's plan includes the feature or if the project is public. |
 | `commit_email_hostname`                  | string           | no                                   | Custom hostname (for private commit emails). |
 | `container_registry_token_expire_delay`  | integer          | no                                   | Container Registry token duration in minutes. |

ee/app/helpers/ee/application_settings_helper.rb

@@ -20,6 +20,7 @@ module EE
     def visible_attributes
       super + [
         :allow_group_owners_to_manage_ldap,
+        :automatic_purchased_storage_allocation,
         :check_namespace_plan,
         :elasticsearch_aws,
         :elasticsearch_aws_access_key,

ee/app/models/ee/application_setting.rb

@@ -105,6 +105,7 @@ module EE
       def defaults
         super.merge(
           allow_group_owners_to_manage_ldap: true,
+          automatic_purchased_storage_allocation: false,
           custom_project_templates_group_id: nil,
           default_project_deletion_protection: false,
           deletion_adjourned_period: DEFAULT_NUMBER_OF_DAYS_BEFORE_REMOVAL,