Add an index page for the API integration

This commit adds a placeholder page which, for now, just has links to
the API keys page and links to the clients.

There’s more stuff to come on this page, but this commit just does the
reorganising so that it’s easier to review.

tests/app/main/views/test_api_keys.py

@@ -1,10 +1,26 @@
 import uuid
 
 from flask import url_for
+from bs4 import BeautifulSoup
 
 from tests import validate_route_permission
 
 
+def test_should_show_api_page(
+    app_,
+    mock_login,
+    api_user_active,
+    mock_get_service,
+    mock_has_permissions
+):
+    with app_.test_request_context(), app_.test_client() as client:
+        client.login(api_user_active)
+        response = client.get(url_for('main.api_integration', service_id=str(uuid.uuid4())))
+        assert response.status_code == 200
+        page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
+        assert page.h1.string.strip() == 'API integration'
+
+
 def test_should_show_empty_api_keys_page(app_,
                                          api_user_pending,
                                          mock_login,

tests/app/main/views/test_dashboard.py

@@ -342,7 +342,7 @@ def test_menu_manage_api_keys(mocker,
         assert url_for('main.service_settings', service_id=service_one['id']) not in page
         assert url_for('main.show_all_services') not in page
 
-        assert url_for('main.api_keys', service_id=service_one['id']) in page
+        assert url_for('main.api_integration', service_id=service_one['id']) in page
 
 
 def test_menu_all_services_for_platform_admin_user(mocker,