Make `staticfiles_storage` a public API

[Aymeric Augustin]

This is a follow-up ticket to #23506, focused on the part of the problem I believe we need to solve.

Django should provide a way to obtain the URL of static files other than the {% static %} template tag. I haven't found one in the docs.

I think the easiest solution is to make django.contrib.staticfiles.storage.staticfiles_storage a public API and document that it implements the file storage API, especially the ​url method.

[Tim Graham]

For this it would be helpful to point to docs/howto/custom-file-storage.txt which lists the usual methods for storage classes. For example, staticfiles_storage.url('foo.js') works to get URL.

[Pablo Montepagano]

I don't believe there's much improvement to be made here. In the section "Other Helpers" of docs/ref/contrib/staticfiles.txt we already have this sentence:

The builtin template tag static which takes a path and urljoins it with the static prefix STATIC_URL. If django.contrib.staticfiles is installed, the tag uses the url() method of the STATICFILES_STORAGE instead.

[Mariusz Felisiak]

Replying to Pablo Montepagano:

I don't believe there's much improvement to be made here. In the section "Other Helpers" of docs/ref/contrib/staticfiles.txt we already have this sentence:

The builtin template tag static which takes a path and urljoins it with the static prefix STATIC_URL. If django.contrib.staticfiles is installed, the tag uses the url() method of the STATICFILES_STORAGE instead.

Agreed, this has already been documented in cf546e11ac76c8dec527e39ff8ce8249a195ab42.