Feat/sponsor process first iteration

CHANGELOG:

### Added
- [#804](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/804) Add migration to compute sponsorship hash in existent coop candidates

### CHANGED
- [#796](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/796) Inactive sponsees don't count and are highlighted
- [#801](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/801) Draft subscription requests count for sponsor limit

### Fixed
- [#803](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/803) [#799](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/799) [#795](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/795) Add sponsorship_hash logic to coop_candidates

Related card: https://trello.com/c/V6kjDaw0/1227-implementar-gesti%C3%B3n-de-apadrinamientos

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