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.

首先，按照链接的无密码 Spring 数据库指南，在使用 Standard 消费计划和专用计划的 Azure Spring Apps 服务中重现该故障。比较 `az spring app identity assign`、`force-set` 和 REST API 的行为。当可以分配应用身份，并且可以通过 CLI、REST API 或门户看到该更改时，即表示完成。

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