Cannot connect to server behind self signed certificate on Android

[tschan]

Describe the bug
Even though this problem should be fixed according to #255 I still cannot connect to a Tachidesk server that sits behind a reverse proxy using a self signed certificate. The CA which created this certificate is added to the Android user certificate store. "Open in WEB" works without a problem with Firefox.

To Reproduce
Steps to reproduce the behavior:

1. Setup reverse proxy with self signed certificate
2. Add CA of certificate to Android user certificate store
3. Add server URL with "https://..." to settings
4. "Check your internet connection" error is shown

Expected behavior
Sorayomi should correctly connect to the server.

Screenshots
If applicable, add screenshots to help explain your problem.

Device information (Server)

• Tachidesk version: v1.1.1
• Server Operating System: NixOS (using Docker)
• Server Desktop Environment: N/A
• Server JVM version: whatever comes bundled in Docker image

Device information (Client)

• Client version: v0.5.23
• Client Type: Android
• Client Operating System: Android 9
• Client Specifications: HUAWEI MediaPad M5 (EMUI version 9.1.0)

[tschan]

Looks to me that resolving this hinges on this issue in Dart itself: dart-lang/sdk#50435