[18.0][IMP] subscription_oca: Add automatic recurring payment

[chrisandrewmann]

Adds automatic recurring payment to subscription_oca. When enabled, a subscription charges the customer's saved payment token on each billing run, removing the manual collection step for merchant-initiated recurring payments (stored card, BACS/SEPA direct debit, etc. via a tokenizing payment provider).

Purpose

subscription_oca could only generate invoices; collecting payment was always manual. This closes that gap while guaranteeing a customer is never sent an invoice for money that has not actually been collected.

Changes

• Charge before posting. The invoice is kept in draft and is only posted and reconciled once the payment succeeds. A failed charge never posts an owed invoice and never consumes an invoice number.
• New field Automatic payment boolean on the subscription template, compatible with every invoicing mode (including Draft for silent billing).
• New Payment Token field on the subscription: suggested from the partner's most recent token, constrained to the same commercial partner, and carried over automatically from the originating eCommerce or initial portal sale order payment.
• Success: invoice posted, reconciled, and (per invoicing mode) the paid invoice emailed — never an "amount due" document.
• Asynchronous capture: transaction left pending, invoice posted later on provider webhook confirmation; billing continues normally.
• Failure: invoice stays draft, subscription flagged with Payment Exception, a to-do activity is raised (visible in list/kanban), and the next invoice date is not advanced so the period is retried after a fix.
• The cron skips flagged subscriptions and isolates each one in a savepoint so a single rejected charge can't roll back the batch. Payment Exception is a public field so external retry integrations can set/clear it.
• Add tests for the success, pending, failure, retry and silent-draft paths.
• New manifest dependency: account_payment.
• Version bumped minor: 18.0.1.0.0 → 18.0.2.0.0.
• Added updated USAGE.md - See usage guide for manual testing

Invoicing mode behaviour with automatic payment

Invoicing mode	On a successful charge
Draft	Invoice posted, no email (silent background billing)
Invoice	Invoice posted, paid invoice emailed
Invoice & send	Invoice posted, paid invoice emailed
Sale order & Invoice	Sale order confirmed, invoice posted (no email)

History

This supersedes and improves upon #1331 (an 16.0 PR by @adasatorres, which stuck open with unresolved test failures). It is a fresh 18.0 implementation that keeps the spirit — automatic token-based collection on the billing cron — while addressing its main limitations:

• auto_create_payment boolean instead of a new invoicing-mode option, so automatic payment composes with every mode
  (including Draft for silent billing) rather than being one mode.
• Charge before posting: [16.0][IMP] subscription_oca: recurrent payment #1331 posts and sends the invoice and then marks it paid (or sends it for manual payment when no token exists); here the invoice stays in draft until the charge succeeds, so a failed charge never posts an
  owed invoice, never burns an invoice number, and the customer is never sent an "amount due" document for money already taken.
• Explicit failure handling: a payment_exception flag, a to-do activity in list/kanban, an unchanged next-invoice date for retry, and a cron that skips flagged subscriptions — instead of silently falling back to manual collection.
• Robustness: per-subscription savepoint isolation in the cron, support for asynchronous (pending) capture posted on webhook confirmation, automatic token hand-off from the originating sale order.

Credit to @adasatorres for the original PR

[chrisandrewmann]

@tarteo @yvaucher @carlos-domatix @rousseldenis

Would appreciate your input in testing and hopefully getting merged this time around! I think it's a feature we've all needed for a while.