General source code refactoring

src/shared/messages.js

@@ -0,0 +1,12 @@
+/** Stable wire names. All payloads remain plain, serializable objects. */
+function createMessageTypes() {
+  return Object.freeze({
+    getXsrfToken: "opportunitiesExtension.getXsrfToken",
+    refreshXsrfCookie: "opportunitiesExtension.refreshXsrfCookie",
+    requestOpptyProducts: "opportunitiesExtension.requestOpptyProducts",
+    opptyProductsProgress: "opportunitiesExtension.opptyProductsProgress",
+    requestConsumerTokenService: "opportunitiesExtension.requestConsumerTokenService",
+    requestAccountPlans: "opportunitiesExtension.requestAccountPlans",
+    requestConsumptionTrend: "opportunitiesExtension.requestConsumptionTrend"
+  });
+}