Add modsecurity_enabled to ingress applications

Adds new column to track user setting determining whether to
install modsecurity along with ingress managed application

See https://gitlab.com/gitlab-org/gitlab/issues/39140 for more details

changelogs/unreleased/39140-scope-modsec-feature-flag-to-groups.yml

+---
+title: Add modsecurity_enabled setting to managed ingress
+merge_request: 21968
+author:
+type: added

db/migrate/20191217212348_add_modsecurity_enabled_to_ingress_application.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddModsecurityEnabledToIngressApplication < ActiveRecord::Migration[5.2]
+  DOWNTIME = false
+
+  def up
+    add_column :clusters_applications_ingress, :modsecurity_enabled, :boolean
+  end
+
+  def down
+    remove_column :clusters_applications_ingress, :modsecurity_enabled
+  end
+end

db/schema.rb

@@ -1163,6 +1163,7 @@ ActiveRecord::Schema.define(version: 2019_12_18_225624) do
     t.text "status_reason"
     t.string "external_ip"
     t.string "external_hostname"
+    t.boolean "modsecurity_enabled"
     t.index ["cluster_id"], name: "index_clusters_applications_ingress_on_cluster_id", unique: true
   end