Implement gateway_images_enabled flag

* Replace the existing env var based flag with a shiny new openfeature
  one

This is a basic test implementation that will apply accross all
environments currently

Author: gpeng

manage_breast_screening/mammograms/tests/views/test_appointment_workflow_views.py

@@ -242,10 +242,12 @@ def test_creates_gateway_action(
         mock_send_action.assert_called_once_with(relay, action)
 
     def test_redirects_to_gateway_images_when_enabled(
-        self, clinical_user_client, monkeypatch, confirmed_identity_appointment
+        self, clinical_user_client, with_flag_enabled, confirmed_identity_appointment
     ):
-        monkeypatch.setenv("GATEWAY_IMAGES_ENABLED", "true")
-        RelayFactory.create(setting=confirmed_identity_appointment.clinic_slot.clinic.setting)
+        with_flag_enabled("gateway_images")
+        RelayFactory.create(
+            setting=confirmed_identity_appointment.clinic_slot.clinic.setting
+        )
 
         with patch(
             "manage_breast_screening.gateway.relay_service.RelayService.send_action"

manage_breast_screening/mammograms/views/__init__.py

@@ -1,10 +1,11 @@
-import os
+from openfeature import api
 
 from manage_breast_screening.gateway.models import Relay
 
 
 def gateway_images_enabled(appointment):
     """Check if automatic gateway image retrieval is enabled."""
-    if os.getenv("GATEWAY_IMAGES_ENABLED", "false").lower() == "true":
+    feature_flags = api.get_client()
+    if feature_flags.get_boolean_value("gateway_images", False):
         return Relay.for_appointment(appointment) is not None
     return False

manage_breast_screening/tests/system/clinical/test_gateway_images.py

@@ -1,5 +1,4 @@
-import os
-
+import pytest
 from django.urls import reverse
 from playwright.sync_api import expect
 
@@ -18,6 +17,10 @@
 
 
 class TestGatewayImages(SystemTestCase):
+    @pytest.fixture(autouse=True)
+    def flags(self, with_flag_enabled):
+        self.with_flag_enabled = with_flag_enabled
+
     def test_renders_no_images_content(self):
         self.given_i_am_logged_in_as_a_clinical_user()
         self.and_there_is_an_appointment()
@@ -63,7 +66,7 @@ def and_there_is_an_appointment(self):
         )
 
     def and_gateway_images_are_enabled(self):
-        os.environ["GATEWAY_IMAGES_ENABLED"] = "true"
+        self.with_flag_enabled("gateway_images")
         RelayFactory(setting=self.appointment.clinic_slot.clinic.setting)
 
     def when_i_visit_the_take_images_page(self):