Add account migration UI (#11846)

Fix #10736

- Change data export to be available for non-functional accounts
- Change non-functional accounts to include redirecting accounts

app/models/form/migration.rb

@@ -1,25 +0,0 @@
-# frozen_string_literal: true
-
-class Form::Migration
-  include ActiveModel::Validations
-
-  attr_accessor :acct, :account
-
-  def initialize(attrs = {})
-    @account = attrs[:account]
-    @acct    = attrs[:account].acct unless @account.nil?
-    @acct    = attrs[:acct].gsub(/\A@/, '').strip unless attrs[:acct].nil?
-  end
-
-  def valid?
-    return false unless super
-    set_account
-    errors.empty?
-  end
-
-  private
-
-  def set_account
-    self.account = (ResolveAccountService.new.call(acct) if account.nil? && acct.present?)
-  end
-end