Xendit replaced the single "Invoices paid" webhook field with separate
v3 event groups (Payment tokens v3 / Payment requests v3). Databases
that had Xendit configured before this change stop receiving payment
and card token status updates until the Xendit Dashboard is updated
with the new fields.

Hook into the daily autovacuum cron instead of a dedicated one or an
upgrade-triggered migration script: SaaS/.sh don't force module
upgrades, so a migration script would only catch the providers,
companies, and admins that existed at the exact moment of the upgrade,
and a dedicated ir.cron record wouldn't exist on already-installed
databases until then either. @api.autovacuum methods are discovered
directly from the Python class, so they run immediately everywhere,
keep covering providers and admins added later, and can be removed
later by deleting the method, with no leftover cron record to clean up
through a migration.

For the same reason, track whether admins were already notified by
checking for an existing pending activity instead of adding a stored
field on payment.provider: a new column wouldn't exist either on
databases where the module isn't upgraded, and the ORM would error on
any domain filtering on it.

Notify base.group_system, account.group_account_manager, and
sales_team.group_sale_manager rather than only Sales admins: those are
the groups actually granted write access to payment.provider and its
Xendit credential fields, or otherwise likely to own the provider's
configuration, and covering all three means databases using Xendit
without the Sales app installed (e.g. through Invoicing or Point of
Sale) still have someone to notify. A user in more than one of these
groups is only notified once.

The activity note explains why the change is needed and links the
"webhook configuration" and "Xendit Dashboard" mentions inline to the
Odoo documentation and to the Xendit Dashboard's webhook settings,
respectively, calling out the October 1, 2026 date after which the old
webhook field stops being honored.

Task-6373405

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