Fix/check sponsor for coop candidates

CHANGELOG:

### Fixed
- [#795](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/795) Add sponsorship_hash logic to coop_candidates

Related card: https://trello.com/c/TEINDO5H/1236-merged-api-apadrinamiento-ver-si-socio-puede-apadrinar

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