Feature/ogc 1896 mark invalid email addresses

[Tschuppi81]

Please fill in the commit message below and work through the checklist. You can delete parts that are not needed, e.g. the optional description, the link to a ticket or irrelevant options of the checklist.

Commit message

:

TYPE: <Feature|Performance|Bugfix>
LINK:
HINT:

Checklist

• I have performed a self-review of my code
• I considered adding a reviewer
• I have added an upgrade hint such as data migration commands to be run
• I have updated the PO files
• I have added new modules to the docs
• I made changes/features for both org and town6
• I have updated the election_day API docs
• I have tested my code thoroughly by hand
  • I have tested styling changes/features on different browsers
  • I have tested javascript changes/features on different browsers
  • I have tested database upgrades
  • I have tested sending mails
  • I have tested building the documentation
• I have added tests for my changes/features
  • I am using freezegun for tests depending on date and times
  • I considered using browser tests für javascript changes/features
  • I have added/updated jest tests for d3rendering (election_day, swissvotes)

[linear]

OGC-1896 Newsletter unzustellbare E-Mail-Adressen anzeigen

[Tschuppi81]

wrong ticket in branch name