Add domain test as well

Author: sam-gc

packages-exp/auth-exp/src/core/auth/register.ts

@@ -64,6 +64,8 @@ export function registerAuth(clientPlatform: ClientPlatform): void {
             AuthErrorCode.INVALID_API_KEY,
             { appName: app.name }
           );
+          // Auth domain is optional if IdP sign in isn't being used
+          _assert(!(authDomain?.includes(':')), AuthErrorCode.ARGUMENT_ERROR, {appName: app.name});
           const config: ConfigInternal = {
             apiKey,
             authDomain,