refactor(in-person): convert server error view to CBV

Author: lalver1

benefits/in_person/urls.py

@@ -47,5 +47,5 @@
         admin.site.admin_view(views.SwitchioGatewayUrlView.as_view()),
         name=routes.name(routes.IN_PERSON_ENROLLMENT_SWITCHIO_GATEWAY_URL),
     ),
-    path("error/", admin.site.admin_view(views.server_error), name=routes.name(routes.IN_PERSON_SERVER_ERROR)),
+    path("error/", admin.site.admin_view(views.ServerErrorView.as_view()), name=routes.name(routes.IN_PERSON_SERVER_ERROR)),
 ]

benefits/in_person/views.py

@@ -4,7 +4,7 @@
 from django.shortcuts import redirect
 from django.template.response import TemplateResponse
 from django.urls import reverse
-from django.views.generic import FormView
+from django.views.generic import FormView, TemplateView
 
 from benefits.core.models.transit import TransitAgency
 from benefits.core import models, session
@@ -126,15 +126,20 @@ def get_origin_url(self):
         return reverse(routes.ADMIN_INDEX)
 
 
-def server_error(request):
+class ServerErrorView(mixins.CommonContextMixin, AgencySessionRequiredMixin, TemplateView):
     """View handler for errors caused by a misconfiguration or bad request."""
-    agency = session.agency(request)
-    context = {
-        **admin_site.each_context(request),
-        "title": f"{agency.long_name} | In-person enrollment | {admin_site.site_title}",
-    }
 
-    return TemplateResponse(request, "in_person/enrollment/server_error.html", context)
+    template_name = "in_person/enrollment/server_error.html"
+
+    def get(self, request, *args, **kwargs):
+        return super().get(request, *args, **kwargs)
+
+    def post(self, request, *args, **kwargs):
+        # the Javascript in in_person/index_littlepay.html sends a form POST to this view
+        # rather than implementing this view as a FormView, which requires instantiating the
+        # enrollment.forms.CardTokenizeFailForm, we implement post() to simply return the template via get()
+        # we thus avoid interfering with the view's lifecycle and dispatch() method
+        return super().get(request, *args, **kwargs)
 
 
 def success(request):

tests/pytest/in_person/test_views.py

@@ -194,14 +194,16 @@ def test_get_origin_url(self, view):
 
 
 @pytest.mark.django_db
-@pytest.mark.usefixtures("mocked_session_flow", "mocked_session_agency")
-def test_server_error(admin_client):
-    path = reverse(routes.IN_PERSON_SERVER_ERROR)
-
-    response = admin_client.get(path)
+class TestServerErrorView:
+    @pytest.fixture
+    def view(self, app_request, model_LittlepayConfig):
+        v = views.ServerErrorView()
+        v.setup(app_request)
+        v.agency = model_LittlepayConfig.transit_agency
+        return v
 
-    assert response.status_code == 200
-    assert response.template_name == "in_person/enrollment/server_error.html"
+    def test_view(self, view: views.ServerErrorView):
+        assert view.template_name == "in_person/enrollment/server_error.html"
 
 
 @pytest.mark.django_db