Fix for Blog not allowing publishing, editing and deleting

What does this MR do?

This MR fixes a bunch of bugs in the blog module, that currently prevent blog posts being published, edited and deleted, based on this discussion in Slack: https://yunity.slack.com/archives/C1T1ZM9A4/p1580920032295100

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

Should break nothing.

Links to related issues

https://yunity.slack.com/archives/C1T1ZM9A4/p1580920032295100

How to test

Steps a reviewer can take to verify that this MR does what it says it does e.g.

1. Checkout branch locally
2. Login as Orga
3. Publish a blog post
4. Edit a blog post
5. Delete a blog post

Screenshots (if applicable)

Any relevant screenshots if this is a design / frontend change

Checklist

• 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))
• Once your MR has been merged, you are responsible to update the #foodsharing-beta Slack channel about what has been changed here. They will test your work in different browsers, roles or other settings