Refactor API URLs to use GlobalConstants and update CORS configurations for production

jambotron-ui/src/app/global-constants.ts

@@ -0,0 +1,15 @@
+import {environment} from '../environments/environment';
+
+export class GlobalConstants {
+
+  public static readonly API_URL = (() => {
+    // ... calculate the value and return it
+
+    if(environment.production) {
+      return `${environment.host_name}/api`;
+    }else {
+       return `${environment.host_name}:${environment.port}/api`;
+    }
+
+  })();
+}