Add pagination to Contract API

CHANGELOG:

### CHANGED
- [#908](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/908) Add pagination to Contract API

Related card: https://trello.com/c/Hc6KAjN5/1410-contractes-odoo-per-ov-paginaci%C3%B3

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