Genereate uuids for existing info fields.

priv/repo/migrations/20181201104428_add_uuid_extension.exs

+defmodule Pleroma.Repo.Migrations.AddUUIDExtension do
+  use Ecto.Migration
+
+  def change do
+    execute("create extension if not exists \"uuid-ossp\"")
+  end
+end

priv/repo/migrations/20181201105617_add_uui_ds_to_user_info.exs

+defmodule Pleroma.Repo.Migrations.AddUUIDsToUserInfo do
+  use Ecto.Migration
+
+  def change do
+    execute("update users set info = jsonb_set(info, '{\"id\"}', to_jsonb(uuid_generate_v4()))")
+  end
+end