Sets @auth_callback as an authentication-handling callback for
@domain. Whenever a request comes in to @domain which cannot be
authenticated via a domain-specific auth callback (eg,
#SoupAuthDomainDigestAuthCallback), the generic auth callback
will be invoked. See #SoupAuthDomainGenericAuthCallback for information
on what the callback should do.
Sets @auth_callback as an authentication-handling callback for @domain. Whenever a request comes in to @domain which cannot be authenticated via a domain-specific auth callback (eg, #SoupAuthDomainDigestAuthCallback), the generic auth callback will be invoked. See #SoupAuthDomainGenericAuthCallback for information on what the callback should do.