WIP: Resolve "unverified foodsavers should not be able to post in forums"

Closes ___ (e.g. #230 (closed))

What does this MR do?

Prevent Spam by making sure that only verified users are allowed to post messages

How confident are you it won't break things if deployed?

Not at all

Links to related issues

Checklist (In Progress)

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))