Hi Guys,
after two days trying to figure out why my app doesn't call apple-app-site-association file and safari doesn't recognise that there is an app for this website I finally have figured it out.
So in order to make universal links to work on your website you need
- Associated Domains on developer.apple.com
- to enable Associated Domains in Entitlements.plist
- add your's website domain as applinks:www.mydomain.com
- create apple-app-site-association (you have plenty explanations online)
- And the most import why I lost 2 days of work in IOS Bundle Signing make sure Entitlements.plist is selected under Custom Entitlements!
without this it will not work 
Hope this will be helpful to someone
Chears