feat: ensure client is registered for authorize view

currently the only way to get to the authorize view is from the login
view, so the client should already be registered. But it doesn't hurt
to call it here either.

benefits/oauth/views.py

@@ -44,7 +44,7 @@ def login(request):
 def authorize(request):
     """View implementing OIDC token authorization."""
     verifier = session.verifier(request)
-    oauth_client = oauth.create_client(verifier.auth_provider.client_name)
+    oauth_client = register_provider(oauth, verifier.auth_provider)
 
     if not oauth_client:
         raise Exception(f"oauth_client not registered: {verifier.auth_provider.client_name}")