Add support to load settings from options (flag) and default to specific options

Summary: This change gives priority to a user option settingsString to set up the flipper-server configuration and load them from a json string. Also giving the user the chance to avoid flipper-server looking at the launcher config files in the computer

Reviewed By: mweststrate

Differential Revision: D34210110

fbshipit-source-id: 9e852b79da106b5140c59116fd7d0c0f3155e620

desktop/flipper-server-core/src/utils/launcherSettings.tsx

@@ -65,7 +65,13 @@ function deserialize(content: string): LauncherSettings {
   };
 }
 
-export async function loadLauncherSettings(): Promise<LauncherSettings> {
+export async function loadLauncherSettings(
+  enableLauncherSettings: boolean = true,
+): Promise<LauncherSettings> {
+  if (!enableLauncherSettings) {
+    return defaultLauncherSettings;
+  }
+
   const fileName = getLauncherSettingsFile();
   try {
     const content = (await fs.readFile(fileName)).toString();