Start a process to ingest images from our ceph server

Depends backend#1051 (closed)
Depends backend#1052 (closed)
Depends backend#1053 (closed)

Once we have all 3 endpoints to view buckets & create a process, we need a new user interface to configure and trigger the process.

The UI will be available as /process/bucket/:corpus_id and accessible from the actions menu of a corpus as "Import from bucket".

A first <select> allows the user to pick a bucket. If the ListBuckets endpoint returns a 403, the whole UI is blocked, and a warning is shown "You do not have access to this feature. Please contact the instance administrator".

Once a bucket is selected, a text input is enabled and allow a user to input a Ceph prefix (like path/to/...); no leading /.

The current folder must be clearly indicated (using breadcrumb if you are fancy): this is what will be sent to the API to start the process.

Finally, a button must allow the user to open an optional Folder picker in order to select a folder where the files would be ingested.

A large button must allow a user to start the process with the different selected parameters