[FIX] energy_communities: demo data user unable to acces own partner.

There was a bug that caused that the users created from the demo data were unable to access his own partner.

This was caused because we applied some restrictions to partners of users, so it can only be accessible from the users own company_ids and not all as is intended by Odoo. See !83 (merged) for analysis of the problem and solution.

The solution applied is the executing the function that was created to assign to all partners with users the company_ids that it has access.