[#32] Improvement of errors display in CLI and GUI

[pylapp]

Description

Errors management and display can be improved in both CLI and GUI.
Errors returned by GitHub API were opaque: no HTTP code, no body. Thus some errors were hidden,
even if the origin was the API results.

RepoAlerts has been updated to bring the error message to the frontend.
HTTP errors management has been reviews with better JSON processing with serde.
Add in the GUI a new badge for error cases (red).

Fixes #32

Now the logs can expose better details:

[Orange-OpenSource/ouds-ios] GitHub API error: HTTP 403 — {"message":"Dependabot alerts are disabled for this repository.","documentation_url":"https://docs.github.com/rest/dependabot/alerts#list-dependabot-alerts-for-a-repository","status":"403"}

And the GUI uses a better display for errors with red badges:

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

Checklist:

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have run tests (npm run test) that prove my fix is effective or that my feature works