🔧(backend) add view to manage footer json

We added the `FRONTEND_URL_JSON_FOOTER` environment
variable. It will give the possibility to generate
your own footer content in the frontend.
If the variable is not set, the footer will not
be displayed.

src/backend/core/tests/test_api_footer.py

@@ -0,0 +1,81 @@
+"""Test the footer API."""
+
+import responses
+from rest_framework.test import APIClient
+
+
+def test_api_footer_without_settings_configured(settings):
+    """Test the footer API without settings configured."""
+    settings.FRONTEND_URL_JSON_FOOTER = None
+    client = APIClient()
+    response = client.get("/api/v1.0/footer/")
+    assert response.status_code == 200
+    assert response.json() == {}
+
+
+@responses.activate
+def test_api_footer_with_invalid_request(settings):
+    """Test the footer API with an invalid request."""
+    settings.FRONTEND_URL_JSON_FOOTER = "https://invalid-request.com"
+
+    footer_response = responses.get(settings.FRONTEND_URL_JSON_FOOTER, status=404)
+
+    client = APIClient()
+    response = client.get("/api/v1.0/footer/")
+    assert response.status_code == 200
+    assert response.json() == {}
+    assert footer_response.call_count == 1
+
+
+@responses.activate
+def test_api_footer_with_invalid_json(settings):
+    """Test the footer API with an invalid JSON response."""
+    settings.FRONTEND_URL_JSON_FOOTER = "https://valid-request.com"
+
+    footer_response = responses.get(
+        settings.FRONTEND_URL_JSON_FOOTER, status=200, body="invalid json"
+    )
+
+    client = APIClient()
+    response = client.get("/api/v1.0/footer/")
+    assert response.status_code == 200
+    assert response.json() == {}
+    assert footer_response.call_count == 1
+
+
+@responses.activate
+def test_api_footer_with_valid_json(settings):
+    """Test the footer API with an invalid JSON response."""
+    settings.FRONTEND_URL_JSON_FOOTER = "https://valid-request.com"
+
+    footer_response = responses.get(
+        settings.FRONTEND_URL_JSON_FOOTER, status=200, json={"foo": "bar"}
+    )
+
+    client = APIClient()
+    response = client.get("/api/v1.0/footer/")
+    assert response.status_code == 200
+    assert response.json() == {"foo": "bar"}
+    assert footer_response.call_count == 1
+
+
+@responses.activate
+def test_api_footer_with_valid_json_and_cache(settings):
+    """Test the footer API with an invalid JSON response."""
+    settings.FRONTEND_URL_JSON_FOOTER = "https://valid-request.com"
+
+    footer_response = responses.get(
+        settings.FRONTEND_URL_JSON_FOOTER, status=200, json={"foo": "bar"}
+    )
+
+    client = APIClient()
+    response = client.get("/api/v1.0/footer/")
+    assert response.status_code == 200
+    assert response.json() == {"foo": "bar"}
+    assert footer_response.call_count == 1
+
+    response = client.get("/api/v1.0/footer/")
+    assert response.status_code == 200
+    assert response.json() == {"foo": "bar"}
+    # The cache should have been used
+    assert footer_response.call_count == 1