refactor(enrollment): implement enrollment using Backoffice API

add handling for known case that should be treated as a success

benefits/enrollment/views.py

@@ -9,6 +9,7 @@
 from django.urls import reverse
 from django.utils.decorators import decorator_from_middleware
 from littlepay.api.client import Client
+from requests.exceptions import HTTPError
 
 from benefits.core import models, session
 from benefits.core.middleware import (
@@ -17,7 +18,7 @@
     pageview_decorator,
 )
 from benefits.core.views import ROUTE_LOGGED_OUT
-from . import analytics, api, forms
+from . import analytics, forms
 
 
 ROUTE_INDEX = "enrollment:index"
@@ -60,6 +61,7 @@ def index(request):
     session.update(request, origin=reverse(ROUTE_INDEX))
 
     agency = session.agency(request)
+    payment_processor = agency.payment_processor
 
     # POST back after payment processor form, process card token
     if request.method == "POST":
@@ -73,13 +75,34 @@ def index(request):
         logger.debug("Read tokenized card")
         card_token = form.cleaned_data.get("card_token")
 
-        response = api.Client(agency).enroll(card_token, eligibility.group_id)
-        if response.success:
+        client = Client(
+            base_url=payment_processor.api_base_url,
+            client_id=payment_processor.client_id,
+            client_secret=payment_processor.client_secret,
+            audience=payment_processor.audience,
+        )
+        client.oauth.ensure_active_token(client.token)
+
+        funding_source = client.get_funding_source_by_token(card_token)
+
+        try:
+            client.link_concession_group_funding_source(funding_source_id=funding_source.id, group_id=eligibility.group_id)
+        except HTTPError as e:
+            # 409 means that customer already belongs to a concession group.
+            # the response JSON will look like:
+            # {"errors":[{"detail":"Conflict (409) - Customer already belongs to a concession group."}]}
+            if e.response.status_code == 409:
+                analytics.returned_success(request, eligibility.group_id)
+                return success(request)
+            else:
+                analytics.returned_error(request, str(e))
+                raise Exception(f"{e}: {e.response.json()}")
+        except Exception as e:
+            analytics.returned_error(request, e)
+            raise e
+        else:
             analytics.returned_success(request, eligibility.group_id)
             return success(request)
-        else:
-            analytics.returned_error(request, response.message)
-            raise Exception(response.message)
 
     # GET enrollment index
     else: