Draft: feat(ContractContractService): filter out fiber contracts used in OTRS

CHANGELOG:

### Added
- [#936](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/936) When checking for available contract fibers to pack, exclude those already referenced within ChangeTariffTickets in OTRS

Method get_fiber_contracts_to_pack now checks if any of the available (not packed) fiber contracts in Odoo is already referenced as contract to pack with in any ChangeTariffTickets (with bonified mobile products) in OTRS, or referenced as fiber related contract in any mobile lead line with pack product.

Related card: https://trello.com/c/idFy3X4G/1481-filtrar-de-lendpoint-de-fibres-lliures-les-que-estan-referenciades-en-tiquets-dotrs-per-canvis-de-tarifa-a-producte-bonificat

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⚠ Depends on: https://git.coopdevs.org/coopdevs/som-connexio/otrs-somconnexio/-/merge_requests/171