API for adding food share points

What does this MR do?

Adds the endpoint POST /region/{regionId}/foodSharePoints for adding (proposing) a new food share point. The frontend form is still the same and will be changed in !3520.

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

Quite sure. I added unit tests for the usual cases.

Links to related issues

How to test

1. Checkout branch locally
2. Login as foodsaver
3. Go to any region's food share point page and add a new one
4. Fill out and submit the form

When you log in as userfsp1 you can see the proposed food share point and can accept it. Also, if you add a food share point with this user, it should be added immediately.

Screenshots (if applicable)

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• set a "for:" label to indicate who will be affected by this change
• set the "API change" label if changes in the API are not backward compatible
• added to the next milestone (see https://gitlab.com/foodsharing-dev/foodsharing/-/milestones, unless it has a "for:Dev" label)
• added an entry to CHANGELOG.md
• added a short text in the release notes to /release-notes/YYYY-MM.md
• Once your MR has been merged, you are responsible to create a testing issue in the Beta Testing forum: https://foodsharing.de/region?bid=734&sub=forum. Please change the MRs label to "state:Beta testing".
  • Consider writing a detailed description in German.
  • Describe in a few sentences, what should be tested from a user perspective.
  • Also mention different settings (e.g. different browsers, roles, ...) how this change can be tested.
  • Be aware, that also non technical people should understand.