[sbinfo67]

Adds payment_payplug, an online payment provider for Payplug (France), built on the standard payment framework of Odoo 19.

Features

• Card payment through the Payplug hosted payment page (redirect), from the website checkout and the customer portal (invoice payment, payment links).
• Full and partial refunds from Odoo, plus refunds made in the Payplug portal (created in Odoo on notification, without duplicates).
• Webhook (IPN) that never trusts the POST body: the payment is always re-read from the API before changing the transaction state. Idempotent, with amount/currency/reference/mode checks.
• Two authentication methods: API key (JWT or legacy sk_) or OAuth2 client credentials (token cached in memory, renewed before expiry, replayed once on a 401).
• EUR only. No extra Python dependency (requests).
• French translation.

Not in this PR (roadmap in the module): saved cards (one click), instalments, deferred capture, Apple Pay, integrated payment form, authorization-code OAuth2 flow.

Testing

• 69 automated tests (tag payment_payplug) against a fake Payplug server; they pass on Odoo 19 Community. No test calls the real API.
• Tried against the real Payplug API in test mode and then in production: payment of an invoice with 3-D Secure, notification received, partial and full refunds, token refresh.

Author's repository where the module was developed: https://github.com/sbinfo67/odoo-payplug

I could not find a more fitting OCA repository for online payment providers (account-payment is about payment orders/returns); e-commerce already hosts modules extending payment.provider. Happy to move it elsewhere if reviewers prefer.