Extend 403 template to request access

No permission to access this resource
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Next step in the interaction:
Offer an input (button or whatever) to the user to make a request to access the resource.

There can be a number of ways to that.. config setting that shows the request form on all 403s and sends a notification to an (dedicated?) inbox, and/or if the resource has a dedicated inbox....

I said template in the title of this issue, but it'll act more like its own application (so that the server is not expected to process it like an HTML form) that sends a notification.

首先定位当前的 403 模板以及生成该模板的授权路径。在选择请求流程之前，检查服务器如何识别已登录用户、目标资源和任何专用收件箱。完成的标准是：没有权限的用户可以提交访问请求，预期接收者会收到通知，但 payload 使配置和通知设计仍未确定。