[BUG] l10n_it_riba_oca: RiBa collection fees setting not persisted in multi-company

[mmircoli-nexapp]

Module

l10n_it_riba_oca

Current behavior

When configuring the RiBa collection fees service product (due_cost_service_id) in Settings → Accounting → RiBa Collection Fees in a multi-company environment, the setting does not persist correctly.

The value shown in the settings form always reflects the user's main company (self.env.user.company_id), not the company currently selected in the settings form.

Steps to reproduce

1. Have a multi-company setup (Company A, Company B)
2. Log in as a user whose main company is Company A
3. Switch to Company B in the settings
4. Set a product for "RiBa Collection Fees" → Save
5. Reopen settings for Company B → the value shows Company A's setting (or blank)

Root cause

The default_get override in ResConfigSettings (models/account_config.py) hardcodes self.env.user.company_id.due_cost_service_id:

@api.model
def default_get(self, fields_list):
    res = super().default_get(fields_list)
    if res:
        res["due_cost_service_id"] = self.env.user.company_id.due_cost_service_id.id
    return res

This ignores the company_id field on the settings form (which reflects the company being configured). The related="company_id.due_cost_service_id" field already handles reading/writing to the correct company — the default_get override is a legacy pattern that conflicts with this mechanism.

Expected behavior

The setting should correctly read from and write to the company selected in the settings form, working seamlessly in multi-company environments.

Proposed fix

Remove the default_get override entirely. The related field handles everything correctly on its own.

Version

18.0