Install website, create a custom web page, we'll call it page_1. Ensure
you are not in debug mode (go to /web/health?debug=0 to disable it).
Open the web page enabling the debug-mode /page_1?debug=1, the page
opens but the debug mode is disabled.
Because web pages are served using another routing mechanism than
controlers we have to ensure we load the debug query-string in those
mechanisms too.
closesodoo/odoo#85340
Signed-off-by: Romain Derie (rde) <rde@odoo.com>