Include the set labels in the email for newly created issues

When a new issue is created all attached labels should be shown.

Currently the email contains only:

Foo Bar created an issue: #12345

contents of the issue description…

We are realizing additional information via specific labels. In comparison with bugzilla, it shows many detailed information:

https://example.org/bugzilla/show_bug.cgi?id=12345

            Bug ID: 12345
           Summary: issue title
           Product: `$PROD`
           Version: 1.0
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: `$COMP`
          Assignee: foo@example.com
          Reporter: foo@example.com
        QA Contact: foo@example.com
  Target Milestone: 2.0
          Customer: XXX
         Bug group: Workaround is available, security, usability
       What kind of 
     report is it?: Development Internal
   What type of bug
          is this?: Bug report
        Who will be
   affected by this
              bug?: 1: Will affect a very few installed domains
     How will those 
      affected feel
    about the bug?: 5: Blocking further progress on the daily work