feat: add alternative server for purposes of switching to API v1 (#571)

* feat: add alternative server for purposes of switching to API v1

* fix: naming of next version sync server host variable

app/assets/javascripts/app.ts

@@ -88,7 +88,8 @@ function reloadHiddenFirefoxTab(): boolean {
 
 const startApplication: StartApplication = async function startApplication(
   defaultSyncServerHost: string,
-  bridge: Bridge
+  bridge: Bridge,
+  nextVersionSyncServerHost: string,
 ) {
   if (reloadHiddenFirefoxTab()) {
     return;
@@ -105,6 +106,7 @@ const startApplication: StartApplication = async function startApplication(
     .config(configRoutes)
     .constant('bridge', bridge)
     .constant('defaultSyncServerHost', defaultSyncServerHost)
+    .constant('nextVersionSyncServerHost', nextVersionSyncServerHost)
     .constant('appVersion', bridge.appVersion);
 
   // Controllers
@@ -186,7 +188,8 @@ const startApplication: StartApplication = async function startApplication(
 if (__WEB__) {
   startApplication(
     (window as any)._default_sync_server,
-    new BrowserBridge(__VERSION__)
+    new BrowserBridge(__VERSION__),
+    (window as any)._next_version_sync_server
   );
 } else {
   (window as any).startApplication = startApplication;