Add customizable user roles (#18641)

* Add customizable user roles

* Various fixes and improvements

* Add migration for old settings and fix tootctl role management

db/post_migrate/20220617202502_migrate_roles.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+class MigrateRoles < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  class UserRole < ApplicationRecord; end
+  class User < ApplicationRecord; end
+
+  def up
+    load Rails.root.join('db', 'seeds', '03_roles.rb')
+
+    admin_role     = UserRole.find_by(name: 'Admin')
+    moderator_role = UserRole.find_by(name: 'Moderator')
+
+    User.where(admin: true).in_batches.update_all(role_id: admin_role.id)
+    User.where(moderator: true).in_batches.update_all(role_id: moderator_role.id)
+  end
+
+  def down
+    admin_role     = UserRole.find_by(name: 'Admin')
+    moderator_role = UserRole.find_by(name: 'Moderator')
+
+    User.where(role_id: admin_role.id).in_batches.update_all(admin: true) if admin_role
+    User.where(role_id: moderator_role.id).in_batches.update_all(moderator: true) if moderator_role
+  end
+end