[IMP] energy_selfconsumption: integration invoicing

This is the Trello card

In this branch we worked on the last point of the requirements:

1. Changing the relationship between contract template and self-consumption so that contract template is linked to the product.
2. On the other hand, the obtaining of information is modified so that when the project is activated, contracts are created taking the values ​​stored in self-consumption.

energy_selfconsumption/models/selfconsumption.py

@@ -167,6 +167,10 @@ class Selfconsumption(models.Model):
                 raise ValidationError(_("Project must have a valid CIL."))
             if not record.power or record.power <= 0:
                 raise ValidationError(_("Project must have a valid Rated Power."))
+            if not record.invoicing_mode:
+                raise ValidationError(
+                    _("Project must have defined a invoicing mode before activation.")
+                )
 
             # Create ContractGenerationWizard
             contract_wizard = self.env[