Improve behavior when pasting images on Customer Portal

When customers use the Customer Portal in JIRA Service Desk, they can attach files by pasting the content of the clipboard (CTRL+V in most cases). When a file is pasted this way, it is attached with the name 'image'png'. The issue with this is when more than one image is pasted as each file is named the same, and as we know, JIRA's expected behavior with thumbnails when having several files with the same name will cause all thumbnails to show only one of the images (the most recently attached, see bug ticket JRASERVER-2169). The Customer Portal should be prepared for this.

The suggestion is for the Customer Portal to generate random (or different) names for each image pasted like it already does when attaching an issue from inside JIRA.