defmodule MyApp_7191136.Repo.Migrations.CreateUser do
  use Ecto.Migration

  def change do
    create table(:users) do
      add :name, :string
      add :email, :string
      add :access_token, :string
      add :refresh_token, :string

      timestamps
    end

  end
end

defmodule MyApp_7191136.Repo.Migrations.CreateUser do
  use Ecto.Migration

  def change do
    create table(:users) do
      add :name, :string
      add :email, :string
      add :access_token, :text
      add :refresh_token, :text

      timestamps
    end

  end
end

Use text fields which are unlimited in length rather than the default varchar 255
Use text fields which are unlimited in length rather than the default varchar 255

wsmoak/my_app_7191136