Handle locale redirect

[tobypilling]

We would like to minimize the number of changes and uplifts so it would be great if the server could handle the dynamic locale being included in the URL. This may be necessary anyway, for the case of a missing translated file in the future.

So if this doesn't exist:
https://notifications-stage.thunderbird.net/2.0/eu/notifications.json

Can it just redirect to this:
https://notifications-stage.thunderbird.net/2.0/notifications.json

[tobypilling]

To clarify, we would like to adjust the in-client URL before ESR - so even if the l10n system isn't ready, we could implement this redirect so that we can bake the new URL into the client and simply redirect until the l10n solution is in place.

We'd just need to know what the structure of the URLS will be.

e.g.
https://notifications-stage.thunderbird.net/2.0/en-GB/notifications.json
https://notifications-stage.thunderbird.net/2.0/notifications.json?locale=en-GB
https://notifications-stage.thunderbird.net/2.0/en-GB.json