Alter CustomerInline model and BILLING_STATUS constant

[nascin]

Motivation:

When I list a bill with "frequency": "MULTIPLE_PAYMENTS" and "status": "ACTIVE", a validation error occurs.

Code:

billings = client.billing.list()

Error:

pydantic_core._pydantic_core.ValidationError: 2 validation errors for BillingList
data.6.status
  Input should be 'PENDING', 'EXPIRED', 'CANCELLED', 'PAID' or 'REFUNDED' [type=literal_error, input_value='ACTIVE', input_type=str]
    For further information visit https://errors.pydantic.dev/2.11/v/literal_error
data.6.customer.metadata
  Field required [type=missing, input_value={}, input_type=dict]
    For further information visit https://errors.pydantic.dev/2.11/v/missing

Solution:

• Added the literal 'ACTIVE' to the BILLING_STATUS type.
• Changed the CustomerInline class so the metadata attribute is now optional.

[JoaquimCassano]

lgtm.
Thank's! 🥑