Draft: Feature/cron to notify otrs end of month

CHANGELOG:

### Added
- [#861](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/861) Set a cron to notify OTRS at the end of month

Related card: https://trello.com/c/dhbKxBvd/1372-cron-a-odoo-per-notificar-otrs-a-final-de-mes

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