Support multitenancy in application settings

[m-orlova]

Environment

Jmix version: 2.7.6

Bug Description

Unable to save application settings for a tenant if they are previously saved for other tenant.

Steps To Reproduce

1. Create a Jmix project
2. Add the Application settings and Multitenanct add-ons
3. Add an entity for the custom application settings, e.g. CustomerSettings
4. Add a tenant field to the custom application settings entity
5. Login as a user with one tenant -> Change some property for the created application setting
6. Login as a user with one tenant -> Change the same property for the created application setting and try to save

Current Behavior

An exception occurs:

Expected Behavior

Application settings are saved without errors.

Sample Project

appsettingsmultitenancy.zip