webhook: Switch to authlib for login management
authlib provides a better flask integration.
It also has better support for validating that a user is still authorized for each request.
The mechanism for validating JWT token is not working properly with gitlab. To validate the user, each request that require the logged in user will fetch the user info from the openid server.
Because time is of the essence, I did not improve the login error management, but a start of work can be found there: https://gitlab.apertis.org/infrastructure/qa-report-app/-/commits/wip/detlev/manage-login-errors-better