Security Vulnerabilities in Multivendor Admin - Username Gap and Negative Values in Restaurant Parameters

Describe the bug
When creating a new restaurant in the multivendor admin system, there are serious security vulnerabilities present. The system allows the acceptance of gaps in usernames and negative values in crucial parameters such as delivery time, minimum order, and sales tax, compromising the system's integrity.

To Reproduce
Steps to reproduce the behavior:

Log in to the multivendor admin system.
Navigate to the "Create New Restaurant" section.
Submit the form with a gap in the username field.
Observe that the system accepts the submission without displaying any error messages.
Submit the form with negative values for delivery time, minimum order, and sales tax.
Note that the system also accepts these negative values without proper validation.
Expected behavior

The system should disallow the submission of the form with gaps in the username field, displaying a clear error message.
The system should validate and reject the submission if negative values are provided for delivery time, minimum order, and sales tax, displaying appropriate error messages.
Screenshots
image

Desktop:

Browser: chrome

未指定文件或测试。首先在 multivendor 管理后台的 Create New Restaurant 表单中复现该问题，然后跟踪其对用户名、配送时间、最低订单金额和销售税的验证。用户名中的空格和负参数值能够被拒绝并显示明确的错误信息，即视为完成。

由索引模型根据 Issue 内容生成。