[suggestion] Implement event to change folder name on page creation

I have a client working with the admin plugin and most things are going well except understanding the concept of folder names and what characters to use etc. It is difficult for them to grasp the concept of how filesystems and url's work...

After several emails explaining that they cant use spaces, special characters and uppercases they are having serious issues with this simple concept. I decided to do something about this by creating a plugin that would force the folder name based on a page title but for now this is not possible due to the lack of a proper event to do this.

So my proposition is to implement an event hook that triggers before 'onAdminCreatePageFrontmatter' so the slug of the path can be adjusted by plugins.

Start by tracing the page-creation flow around the onAdminCreatePageFrontmatter event and identify where a preceding hook would be dispatched. Done means plugins can receive that earlier event and adjust the page path slug before the existing frontmatter event runs; no file or test is named in the issue.

Written by the indexing model from the issue text.