Use embeddable text for error pages
Closes #203 (closed)
Use embeddable text on error pages, making them easily editable in admin.
To quickly test these pages, put these URLs in the root urls.py
:
path("400/", TemplateView.as_view(template_name="400.html")),
path("403/", TemplateView.as_view(template_name="403.html")),
path("404/", TemplateView.as_view(template_name="404.html")),
path("500/", TemplateView.as_view(template_name="500.html")),