Display AI rating in the UI

[julien-nc]

As a followup to #408:

• Maybe extend the provider concept so it includes a description and a rating
• Figure out a way to compute the rating in integration_openai depending on the service that is used. We could have a hardcoded list of service URLs for which we know the rating. If an unknown URL is set, we could let the admin set the rating in integration_openai's admin settings.