Reliably set tenant_id for each record

System code has a feature that relies on the field tenant_id to ensure that a record in the database is not leaked to another tenant.

This field is set upon INSERT statement through a DATABASE trigger.

Goal

As INSERT triggers are executed inside the same transaction, and some of them are buggy, it might be better to set this tenant_id by code instead.

Pros:

• Modifying the code is easier than modifying a database trigger
• Usage of DDL statement does not need to deactivate a trigger, which will be much more safe for operations
• It can have better tests per model

Sub-goals

• ability to delete records from the database really reliably. Using only the tenant_id as the source of truth. That will simplify background deletion
• All logic should be readable and testable.