Create table `alerts_service_data`

This table contains data for the `AlertsService` avoiding the usage of
properties.

changelogs/unreleased/generic-alertsettings-model.yml

+---
+title: Create table `alerts_service_data`
+merge_request: 32860
+author:
+type: added

db/migrate/20190906104555_create_alerts_service_data.rb

+# frozen_string_literal: true
+
+class CreateAlertsServiceData < ActiveRecord::Migration[5.2]
+  DOWNTIME = false
+
+  def change
+    create_table :alerts_service_data do |t|
+      t.references :service, type: :integer, index: true, null: false,
+        foreign_key: { on_delete: :cascade }
+      t.timestamps_with_timezone
+      t.string :encrypted_token, limit: 255
+      t.string :encrypted_token_iv, limit: 255
+    end
+  end
+end

db/schema.rb

@@ -26,6 +26,15 @@ ActiveRecord::Schema.define(version: 2019_09_12_061145) do
     t.integer "cached_markdown_version"
   end
 
+  create_table "alerts_service_data", force: :cascade do |t|
+    t.integer "service_id", null: false
+    t.datetime_with_timezone "created_at", null: false
+    t.datetime_with_timezone "updated_at", null: false
+    t.string "encrypted_token", limit: 255
+    t.string "encrypted_token_iv", limit: 255
+    t.index ["service_id"], name: "index_alerts_service_data_on_service_id"
+  end
+
   create_table "allowed_email_domains", force: :cascade do |t|
     t.datetime_with_timezone "created_at", null: false
     t.datetime_with_timezone "updated_at", null: false
@@ -3740,6 +3749,7 @@ ActiveRecord::Schema.define(version: 2019_09_12_061145) do
     t.index ["type"], name: "index_web_hooks_on_type"
   end
 
+  add_foreign_key "alerts_service_data", "services", on_delete: :cascade
   add_foreign_key "allowed_email_domains", "namespaces", column: "group_id", on_delete: :cascade
   add_foreign_key "analytics_cycle_analytics_group_stages", "labels", column: "end_event_label_id", on_delete: :cascade
   add_foreign_key "analytics_cycle_analytics_group_stages", "labels", column: "start_event_label_id", on_delete: :cascade