issue_list: add filter by assignee and author
issue_list: add filter by assignee and author

Different from mr_list, issue_list has no filter by assignee nor author.
This patch adds both using the same logic as done in mr_list.

Signed-off-by: Bruno Meneguele <82c7731bc2625bcbab88bc571aee6631ba3f66f3@redhat.com>

zaquestion/lab,zaquestion/lab