[compass_app] issues when using the compass_app according to the readme

[Rocke1001feller]

There are issues I encounter

• value key can not match: add_guests ---> add-guests; submit_button ---> submit-button;
• integration test failed when using app_server_data_test.dart: which also encounter by #2563

fix these bugs

@ericwindmill please review my PR. https://github.com/flutter/samples/pull/2599