Edi format is going to be removed eventually - `account_edi_proxy_client` should not depend on it and be more flexible in general.
This commit:
- Removes edi_format field from `account_edi_proxy_client.user` model. We still have to add them in `l10n_it_edi` as it still heavily relies on edi format for now.
- Adds a way to have a unique edi user per company, proxy user, edi mode combination.
This is a necessary step before adding peppol, which will also depend on the account_edi_proxy_client
closesodoo/odoo#116059
Related: odoo/upgrade#4458
Signed-off-by: Laurent Smet <las@odoo.com>