Service plan of Tenant does not change

**Describe the bug**
When I use the Edit page of a tenant and want to change the service plan (property `ProductTierId`), it does not change but keep its value.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to the signup admin page
2. Login as Tenant Admin user
3. go to Admin in the top menu
4. Select your Tenant and choose another Service Plan
5. Click Save
6. You will be redirected to the Tenant list overview, but it still holds its old Service Plan. It does not change.

The other properties can be changed but Service Plan cannot. Fun fact: The Edit page will next time you click Edit on the tenant show the value you selected before - not the value as it is represented in the data. But when you open the Detail page of a tenant, you will see the right value. It looks like that the UI control for the Service Plan on the Edit page is not correctly mapped.

**Expected behavior**
The tenant Service Plan should change in the database after change it in the Edit page of a tenant.

**Screenshots**
Tenants overview before editing:

Then I clicked Edit and changed the Service Plan

Its still the same:

**Desktop (please complete the following information):**
- OS: Windows with WSL Debian
- Browser Chrome
- Version 120.0.6099.217

Start at the signup admin Tenant Edit page and trace the ProductTierId value through the save flow, since the issue identifies the service-plan control as incorrectly mapped. Reproduce the change, then verify that the tenant list, Edit page, Detail page, and database all show the selected Service Plan.

Written by the indexing model from the issue text.