# `Accrue.Billable`
[🔗](https://github.com/szTheory/accrue/blob/accrue-v1.0.0/lib/accrue/billable.ex#L1)

One-line macro that makes any host schema billable.

When a host schema calls `use Accrue.Billable`, it gains:

  1. A `has_one :accrue_customer` association scoped by `owner_type`
  2. A `__accrue__(:billable_type)` reflection callback
  3. A `customer/1` convenience that delegates to `Accrue.Billing.customer/1`

## Usage

    defmodule MyApp.User do
      use Ecto.Schema
      use Accrue.Billable

      schema "users" do
        field :email, :string
        timestamps()
      end
    end

## Rename safety

By default, `billable_type` is derived from the last segment of the
module name (`MyApp.User` becomes `"User"`). If you rename the module
later, existing `accrue_customers` rows will have the OLD name in
`owner_type`, causing a mismatch.

Pin the type explicitly if there is any chance of renaming:

    use Accrue.Billable, billable_type: "User"

Changing a module name without pinning `billable_type:` requires a data
migration on `accrue_customers.owner_type`.

## Association notes

The `has_one :accrue_customer` association uses `references: :id` and
`foreign_key: :owner_id` with a `:where` clause filtering by
`owner_type`. Because `accrue_customers.owner_id` is a `:string`
column (to support integer, UUID, and ULID host PKs losslessly), the
association works best with binary/UUID PKs. For integer PKs, the
`Accrue.Billing` context handles the `to_string/1` coercion in its
fetch/create path rather than relying on the association join.

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*Consult [api-reference.md](api-reference.md) for complete listing*