Create copy contract service info when holder change

CHANGELOG:

### Fixed
- [#721](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/721) Create copy contract service info when holder change

Related card: https://trello.com/c/VLs6vfVE/1088-no-podem-editar-servicecontractinfo-si-%C3%A9s-compartit-amb-m%C3%A9s-dun-contracte

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