First step

• A given File upload field can hold more than one file attachment. A user can add another "upload input", part of the same field. A user can also remove an "upload input", while keeping at least one "upload input" per field.
• When uploading a file, it should be split into chunks. The first chunk will be sent using POST /artifact_temporary_files, then the following chunks will be sent using PUT /artifact_temporary_files/:id. The chunks will be appended to the same file.
• When an error occured during an upload, the user can retry uploading.
• A user can remove an uploaded file, which triggers a DELETE /artifact_temporary_files/:id.
• when I click on the modal's "Submit" button, then the list of temporary files' ids will be sent with the PUT /artifacts/:id request. It will bind the files to the artifact.

Second step

• The existing limit (5) on total temporary files should be removed.
• Instead, a new limit should be added: a given user should have a total file size quota that is the sum of all her temporary files' sizes. E.g. with a limit of 64 MB, if userA already has uploaded File1 of 33 MB, userA can upload File2 of 16 MB but cannot upload File3 of 32 MB.
• A new query should be added to the existing REST route GET /artifact_temporary_files. It should respond with the remaining file size quota for the logged user.
• The remaining file size quota for the logged user should be displayed near the file upload field.
• A cron should be added. It will clean up temporary files that are older than (?).