Finish relation definition refactor

[lucasbordeau]

Scope & Context

Frontend, everything related to relation manipulation.

Technical inputs

We implemented a relationDefinition computed field on metadata. We want to use only this field to implement a unique system for relations and remove confusion we easily get when manipulating relations with the current backend.

[greptile-apps]

1. Update field-metadata.resolver.ts to ensure relationDefinition is computed and returned correctly.
2. Modify field-metadata.service.ts to centralize logic for computing relationDefinition.
3. Refactor SettingsObjectNewFieldStep2.tsx to use relationDefinition for all relation manipulations.
4. Update useRelationField.ts to utilize relationDefinition for consistent relation handling.

References