Add a Maintenance Mode Banner

Checks the api for an exisiting Maintenance Mode if it exists display a banner.

Closes CE-2912

src/components/maintenance/MaintenanceMode.js

+import { useContext, useEffect } from "react";
+import { useAPIMethod, MaintenanceModeBanner } from "@ess-ics/ce-ui-common";
+import { apiContext } from "../../api/DeployApi";
+
+export function MaintenanceMode() {
+  const client = useContext(apiContext);
+  const {
+    value: mode,
+    wrapper: getMode,
+    abort: abortGetMode
+  } = useAPIMethod({
+    fcn: client.apis.Maintenance.getCurrentMode,
+    call: false
+  });
+
+  useEffect(() => {
+    getMode();
+    return () => {
+      abortGetMode();
+    };
+  }, [abortGetMode, getMode]);
+
+  if (mode) {
+    return <MaintenanceModeBanner {...mode} />;
+  }
+
+  return;
+}