Consider using `django.http.request.HttpRequest.build_absolute_uri()` to obtain the absolute URI of a resource

[candleindark]

Currently, the constant, django.conf.settings.DANDI_API_URL, is used in generation of the absolute URI of a resource provided by the service, such as:

dandi-archive/dandiapi/api/views/info.py

Line 59 in b9bb183

api_url = f'{settings.DANDI_API_URL}/api'

(For more examples, check out https://github.com/search?q=repo%3Adandi%2Fdandi-archive+%22DANDI_API_URL%22+language%3APython&type=code&l=Python)

This approach relies on django.conf.settings.DANDI_API_URL being set to a value that's accessible to the client making the request and may become an issue if the DANDI Archive service is served through more than one domain. Consider using django.http.request.HttpRequest.build_absolute_uri() to obtain the absolute URI of a resource instead. It obtains an absolute URI based on the incoming request being handled.

Additional context
This issue originates from the discussion at #2386 (comment)