Add inactive sponsored flag to ResPartner

CHANGELOG:

### Added
- [#806](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/806) Add inactive sponsored flag to ResPartner

Related card: https://trello.com/c/dCu62Oas/1269-flag-apadrinada-donada-de-baixa-a-la-fitxe-de-contacte

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