Migrate existing `open_registrations` setting to the new `registrations_mode` (#10269)

* Migrate existing `open_registrations` setting to the new `registrations_mode`

Fixes #10263

* Remove unrelated db changes that have creeped in

db/migrate/20190314181829_migrate_open_registrations_setting.rb

+class MigrateOpenRegistrationsSetting < ActiveRecord::Migration[5.2]
+  def up
+    open_registrations = Setting.find_by(var: 'open_registrations')
+    return if open_registrations.nil? || open_registrations.value
+    setting = Setting.where(var: 'registrations_mode').first_or_initialize(var: 'registrations_mode')
+    setting.update(value: 'none')
+  end
+
+  def down
+    registrations_mode = Setting.find_by(var: 'registrations_mode')
+    return if registrations_mode.nil?
+    setting = Setting.where(var: 'open_registrations').first_or_initialize(var: 'open_registrations')
+    setting.update(value: registrations_mode.value == 'open')
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2019_03_07_234537) do
+ActiveRecord::Schema.define(version: 2019_03_14_181829) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -36,19 +36,6 @@ ActiveRecord::Schema.define(version: 2019_03_07_234537) do
     t.index ["account_id", "domain"], name: "index_account_domain_blocks_on_account_id_and_domain", unique: true
   end
 
-  create_table "account_identity_proofs", force: :cascade do |t|
-    t.bigint "account_id"
-    t.string "provider", null: false
-    t.string "provider_username", null: false
-    t.text "token", null: false
-    t.boolean "proof_valid"
-    t.boolean "proof_live"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.index ["account_id", "provider", "provider_username"], name: "index_account_proofs_on_account_and_provider_and_username", unique: true
-    t.index ["account_id"], name: "index_account_identity_proofs_on_account_id"
-  end
-
   create_table "account_moderation_notes", force: :cascade do |t|
     t.text "content", null: false
     t.bigint "account_id", null: false