Ecto model relationships with non-default column names

ecto_model_relationships_non_defaults.ex

defmodule MyApp.User do
  use MyApp.Web, :model
  @primary_key {:UserId, :id, autogenerate: true}

  schema "user" do
    has_one :credential, MyApp.Credential,
      foreign_key: :UserId,
      references: :UserId
    many_to_many :roles, MyApp.Role,
      join_through: MyApp.UserRole,
      join_keys: [UserId: :UserId, RoleId: :RoleId]
  end
end