Add query handling for custom settings pages

Author: ravewebdev

api/wordpress/_global/getSettingsCustomPage.js

@@ -0,0 +1,21 @@
+import queryError404Page from '../pages/queryError404Page'
+import processPostTypeQuery from './processPostTypeQuery'
+
+/**
+ * Retrieve single page set via Additional Settings.
+ *
+ * @author WebDevStudios
+ * @param {string} page Custom page name in settings.
+ * @return {object}     Object containing Apollo client instance and post data or error object.
+ */
+export default async function getSettingsCustomPage(page) {
+  // Define single page query based on page name.
+  const pageQuery = {
+    404: queryError404Page
+  }
+
+  // Retrieve page query.
+  const query = pageQuery?.[page] ?? null
+
+  return processPostTypeQuery('page', page, query)
+}