[Usability] Human readable Errormessage if Backup/Restore fails with "Authentication failes"

[k3b]

Current situation (as of Sourcecode from 2023-01-30)

if the app-signing-signatures of
privacy-friendly-backup-app and the the client app where the backup should be made of (i.e. https://github.com/SecUSo/privacy-friendly-finance-manager) are not properly set in "assets/Signatures.json" then Backup silently fails without any user feedback in the gui.

The only hint a developper gets is a debug-log-message "D Error: Authentication failed." without any hint how to fix this.

Expected situation

In privacy-friendly-backup there should be some warning message

"Warning: ... . Do you want to continue anyway? yes/No"

Without "Do you want to continue anyway?" the user backup data is useless because there is no way to restore the data.

The README.md of https://github.com/SecUSo/privacy-friendly-backup-api should contain information how to integrate privacy-friendly-backup-api into a client-app and how to setup assets/Signatures.json

How to reproduce

The problem is reproducable if a developper creates a local compilation of privacy-friendly-backup and the client app.

For details and errorlog see SecUSo/privacy-friendly-finance-manager#1 (comment)