Allow to choose the starting date in change tariffs api calls

CHANGELOG:

### Added
- [#740](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/740) Allow to choose the starting date in change tariffs api calls

Related card: https://trello.com/c/ue2yeVNU/1162-permetre-fer-canvis-de-tarifa-per-lapi-dodoo-editant-les-dates-del-canvi

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