Add index for user follower address.

[akkoma] / priv / repo / migrations / 20180325172351_add_follower_address_index_to_users.exs

defmodule Pleroma.Repo.Migrations.AddFollowerAddressIndexToUsers do
  use Ecto.Migration

  @disable_ddl_transaction true
  def change do
    create index(:users, [:follower_address], concurrently: true)
  end
end