For Seahorse, we enabled MOZ_USER_ID to avoid MT auth when only credit card is supported for payments. We need to do the same for US and UK

Any country that doesn't have carrier billing, shouldn't do MT auth.

P1 because its affecting phones shipping this week.

If we make this change to remove MT auth then we will have to remove this piece to enable CB when you do finally launch in the UK and US. This will only impact first time users who might find it being an odd experience but then if they purchase at least once a month then they won't see the MT auth again because of the cookie. Also, I am not sure how this is blocking testing because everything still works just not in the same way as Seahorse. We are working on a wider piece related to this but will not be ready in quick time. When we built Seahorse we created a new network called VEN_MOZ which all users are assigned to regardless but in UK and US because we know which operators they are coming on we don't want to use this same method. But is there any reason why we would develop something for UK and US specific and then switch off when you do wish to launch CB. Please note we are fully connected to all Operators in UK and US and it would be classed as configuration to launch Mozilla on all operators.

I believe we decided that we will use MT auth. Bango can get use header enrichment for US and UK phones, so this comes down to a corner case. It will work much like any other operator billing region.