Cannot assign identities to App in Standard consumption and dedicated plan

**Describe the bug**
Cannot assign system-assigned or user-assigned managed identities to App. Tried Azure CLI and Rest API. `az spring app identity assign` command failed with "Invalid arguments: The Properties must be provided."; `az spring app identity force-set` command succeeded but nothing changed -- no identities were added. Rest API returned 200 but nothing changed as well. My plan is "Standard consumption and dedicated". According to https://learn.microsoft.com/en-us/azure/spring-apps/enterprise/plan-comparison, it should support identities.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to 'Azure Spring Apps' in Azure Portal.
2. Create a service in "Standard consumption and dedicated" plan.
3. Follow this [guide](https://learn.microsoft.com/en-us/azure/developer/java/spring-framework/deploy-passwordless-spring-database-app?toc=%2Fazure%2Fspring-apps%2Fconsumption-dedicated%2Ftoc.json&bc=%2Fazure%2Fspring-apps%2Fconsumption-dedicated%2Fbreadcrumb%2Ftoc.json&tabs=mysql)
4. You should fail at the step where you're to run command `az spring connection create`.
5. You will find you cannot assign any type of identities to the app, no matter what method you try.

**Expected behavior**
Expect to successfully follow the guide link in the step 3 above. Expect to succeed and see the change using CLI or Rest API.

**Screenshots**
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**Additional context**
Add any other context about the problem here.

**Can we contact you for additional details?** Y

If yes, please send us your contact information to AzureSpringCloud-Talk@service.microsoft.com and include the issue number in the email title.

Start by reproducing the failure in an Azure Spring Apps service using the Standard consumption and dedicated plan, following the linked passwordless Spring database guide. Compare `az spring app identity assign`, `force-set`, and the REST API behavior. Done means an app identity can be assigned and the change is visible through the CLI, REST API, or portal.

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