♻️ [open-formulieren/open-forms#4929] Extract form landing page route…

… into separate component

Created a separate component that handles the redirect logic from the
landing page, using the context rather than props to get the
necessary information. This makes it possible to use the component as
element in a statically defined route.

src/components/FormLandingPage.jsx

@@ -0,0 +1,15 @@
+import {Navigate} from 'react-router-dom';
+
+import useFormContext from 'hooks/useFormContext';
+import useInitialDataReference from 'hooks/useInitialDataReference';
+
+const FormLandingPage = () => {
+  const {introductionPageContent = ''} = useFormContext();
+  const {addInitialDataReference} = useInitialDataReference();
+  const startPageUrl = introductionPageContent ? 'introductie' : 'startpagina';
+  return <Navigate replace to={addInitialDataReference(startPageUrl)} />;
+};
+
+FormLandingPage.propTypes = {};
+
+export default FormLandingPage;

src/components/formRoutes.jsx

@@ -0,0 +1,10 @@
+import FormLandingPage from 'components/FormLandingPage';
+
+const formRoutes = [
+  {
+    path: '',
+    element: <FormLandingPage />,
+  },
+];
+
+export default formRoutes;