auth: Refactor how authentication methods are passed to server/auth library.

server/auth/authtest/method.go

Index: server/auth/authtest/method.go
diff --git a/server/auth/authtest/method.go b/server/auth/authtest/method.go
index 6a611a5cad7226851937559d13c7bbfef01d8ba0..3043015d7b39ada621ec824605f1a04392548414 100644
--- a/server/auth/authtest/method.go
+++ b/server/auth/authtest/method.go
@@ -33,10 +33,10 @@ func (m FakeAuth) Authenticate(context.Context, *http.Request) (*auth.User, erro
 
 // LoginURL returns fake login URL.
 func (m FakeAuth) LoginURL(c context.Context, dest string) (string, error) {
-	return "http://fake/login?dest=" + url.QueryEscape(dest), nil
+	return "http://fake.example.com/login?dest=" + url.QueryEscape(dest), nil
 }
 
 // LogoutURL returns fake logout URL.
 func (m FakeAuth) LogoutURL(c context.Context, dest string) (string, error) {
-	return "http://fake/logout?dest=" + url.QueryEscape(dest), nil
+	return "http://fake.example.com/logout?dest=" + url.QueryEscape(dest), nil
 }