Issue Summary

The instructions for CSV imports include examples of attachment address syntax, but do not include the syntax for authenticating with Jira to download the attachments.

Steps to Reproduce

1. Follow the instructions for importing here: https://confluence.atlassian.com/adminjiraserver/importing-data-from-csv-938847533.html
2. Use the example syntax for http/https-based Jira URLs, and modify the csv according to the instructions
3. Perform the import

Expected Results

Attachments will be downloaded

Actual Results

Attachments are not downloaded.  Instead, html error files are downloaded for every attachment because the download requests are not authenticated.

Workaround

We should update the import instructions to include the following syntax, which is included in this Jira cloud KB:

14/Feb/19 3:53 PM;admin;image.png;https://<JIRA-Server-Username>:<JIRA-Server-Password>@myjirasite.com/secure/attachment/10000/image.png 

This syntax is not just for importing into Jira Cloud, but for any import that pulls attachments from any Jira instance where those attachments are not publicly exposed.