Feature Request: Pass custom ACS URL

[henryh9n]

I have a specific use case with my multi-tenant application.
Since we use dynamic routing (with the tenant name in the URL), utils.get_saml_client() function fails to get the proper URL for the ACS endpoint. The get_reverse finds only the base URL (not the one for tenant).
It happens on this line:

django-saml2-auth/django_saml2_auth/saml.py

Line 184 in df32f5f

acs_url = domain + get_reverse([acs, "acs", "django_saml2_auth:acs"]) # type: ignore

For example, let's say the base ACS URL is https://example.com/api/acs. Since we support multiple tenants, https://example.com/api/tenant-1/acs and https://example.com/api/tenant-2/acs are also valid ACS URLs, however Django will only find the base one (due to the way we set it up).

Would be nice to have a feature to be able to set this URL manually, instead of reversing it.
IMO, ideally we can have 2 ways to do it:

1. Static: We set a variable in config which then is used as the ACS URL instead of reverse().
   This would be useful when you have some redirects behind the scene.
2. Dynamic: We can pass a hook function that dynamically determines the URL.
   Useful when you have dynamic routing and multiple ACS URLs for tenants or other purposes

[mostafa]

Hey @henryh9n,

I like the idea the static/dynamic method. We keep backward compatibility while allowing customization of the ACS URL.