/rest/api/latest/user/search api doesn't return all values if username is not specified

Summary

Currently "/rest/api/latest/user/search" API does not return all users if search string is blank:

• /rest/api/latest/user/search?username=

Notes

In various environments, it has been observed that setting username to one of the following characters will do the trick:

• /rest/api/latest/user/search?username="" (double quotes)
• /rest/api/latest/user/search?username='' (single quotes)
• /rest/api/latest/user/search?username=. (dot)
• /rest/api/latest/user/search?username=% (percent)
• /rest/api/latest/user/search?username=_ (underscore)

Also, maxResults and startAt seem to be functioning.

For example, in JIRA 7.3, the following calls will return 5 users starting from the 3rd user in the list:

• http://localhost:8730/jira/rest/api/latest/user/search?username=""&maxResults=5&startAt=2
• http://localhost:8730/jira/rest/api/latest/user/search?username=''&maxResults=5&startAt=2
• http://localhost:8730/jira/rest/api/latest/user/search?username=.&maxResults=5&startAt=2

Replace http://localhost:8730/jira with actual Base URL