Fix SR API to create sponsorship_coop_agreement SR

CHANGELOG:

### Changed
- [#812](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/812) Change SR API to create sponsorship_coop_agreement SR 

Related card: https://trello.com/c/sJ0kFarq/1268-modificaci%C3%B3n-api-subscription-request-create-para-sponsorshipcoopagreement

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