feat: Add NotificationTray persistence by course (#772)

REV-2424

src/data/sessionStorage.js

@@ -0,0 +1,34 @@
+// This file holds some convenience methods for dealing with sessionStorage. Unlike localStorage that never expires,
+// sessionStorage is cleared when the browser tab is closed since the page session ends
+//
+// NOTE: These storage keys are not namespaced.  That means that it's shared for the current fully
+// qualified domain.  Namespacing could be added, but we'll cross that bridge when we need it.
+
+function getSessionStorage(key) {
+  try {
+    if (global.sessionStorage) {
+      const rawItem = global.sessionStorage.getItem(key);
+      if (rawItem) {
+        return JSON.parse(rawItem);
+      }
+    }
+  } catch (e) {
+    // If this fails for some reason, just return null.
+  }
+  return null;
+}
+
+function setSessionStorage(key, value) {
+  try {
+    if (global.sessionStorage) {
+      global.sessionStorage.setItem(key, JSON.stringify(value));
+    }
+  } catch (e) {
+    // If this fails, just bail.
+  }
+}
+
+export {
+  getSessionStorage,
+  setSessionStorage,
+};