Link new fiber contract with existing mobile contracts
CHANGELOG:
### Added
- [#990](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/990) Link new fiber contract with existing mobile contracts
Related card: https://trello.com/c/FcKcY2rx/1538-cas-activaci%C3%B3-de-fibra-amb-m%C3%B2bils
Edited by Gerard Funosas