Download a static file by href, on post request or XMLHttpRequest

## Use case

We have a mobile app and at some point our users need to import some data into our mobile app but to do it
users need to export this data from a 3rd party website first.
So we open a webview to allow our users to still "be inside" of our app, sign in to a 3rd party website and
click on an Export button there to download a file. After that users click on our Import button and imports
the just downloaded file.

## Proposal

Because of there different 3rd party websites they do provide different ways of export.
So it would be really great to have all of them like:

- Download a static file by
- Download on post/get request
- Download on XMLHttpRequest

L’issue non indica file né test. Inizia tracciando la gestione da parte di WebView dei download statici di href, delle richieste POST/GET e di XMLHttpRequest, quindi chiarisci l’ambito delle piattaforme e come i file scaricati dovrebbero diventare disponibili per il flusso Import dell’app. Done dovrebbe coprire i meccanismi di esportazione richiesti con un comportamento documentato e verificabile.

Scritto dal modello di indicizzazione a partire dal testo della issue.