reporting Jira issues back to the ET

[kkaarreell]

What we are currently missing is NEWA updating advisory with a link to the respective Jira issue (epic).
Either having a hard coded message so that users could enable back-reference in the issue-config file with something like update_erratum: True or we could let users provide a custom message. Or maybe both.
Also, we should avoid ET updates when running against the Jira stage instance.