Ensure that the cart can take up to 100 series
For now there is a problem, when adding 95 series in the cart, the download hangs (as reported by a user).
Hint: there may be a mismatch between the default limit of the API and the URL generated by the UI.
Server-side, the limit could be raised to e.g. 1000 series but client-side, the cart being stored in local-storage, we don't know how much data each browser can store. So let's stay with an arbitrary limit of 100 series.
Note: the real solution would be to create a user account, storing the cart contents server-side.