Don't timeout during long imports

Long uploads to S3 via the Web UI fail.

Two different problems have been identified. After some analysis, we believe the following can happen:

1. direct upload sends large files to S3, then the execution of the import is requested to Nuxeo; if the import (FileManager.Import operation) takes longer than the transaction timeout then it will fail.

2. direct upload of large files sends them directly from the browser to S3; while this is ongoing no interactions with the Nuxeo server happen therefore after some time (default 1h) the HTTP session times out; after the direct upload is finished some browser interaction with the server is supposed to happen but fails because there is no session anymore so no authentication and the browser gets a 401 or 403 (prompting for basic auth).

For 1. the solution is to do the import in a transaction with a very long timeout to avoid import timeouts. This ticket will deal with this.

For 2. there is no immediate solution, but a simple workaround is to increase the HTTP session timeout (session.timeout in nuxeo.conf, expressed in minutes; the default is 60).

To completely avoid 2. the UI should have something regular contact with the server while the direct upload is ongoing, to avoid session timeouts. This will have to be the work of another ticket (NXP-28114).