https://www.medo64.com/2014/09/client-authenticated-tls-in-c/
https://docs.microsoft.com/en-us/azure/app-service/app-service-web-configure-tls-mutual-auth
https://docs.microsoft.com/en-us/azure/app-service/app-service-web-ssl-cert-load
https://stackoverflow.com/a/49317930
https://geekflare.com/openssl-commands-certificates/
https://medium.com/@hafizmohammedg/configuring-client-certificates-on-iis-95aef4174ddb
#App Development
https://github.com/ppedvAG/190205_Xamarin_MUC
https://visualstudio.microsoft.com/de/vs/msft-android-emulator/
https://blog.xamarin.com/xamarin-forms-4-0-preview/
https://docs.microsoft.com/de-de/xamarin/xamarin-forms/app-fundamentals/shell?tabs=android
https://blog.xamarin.com/xamarin-forms-4-0-feature-preview-an-entirely-new-point-of-collectionview/
https://referencesource.microsoft.com/
https://github.com/Fody/PropertyChanged
https://docs.microsoft.com/en-us/xamarin/essentials/
Variante "alt": nuget xam.plugin (z.b media für kamera + gallerie)
https://docs.microsoft.com/en-gb/xamarin/android/deploy-test/release-prep/?tabs=windows
https://docs.microsoft.com/en-gb/xamarin/ios/deploy-test/app-distribution/
http://placekitten.com/100/100
https://baconmockup.com/300/200/
http://www.fillmurray.com/g/200/300