Add pickup manual API test, with bugfix and clean up

Closes #1374 (closed)

What does this MR do?

The pickup API for manual pickups is untested and had some bugs (No back request messages, 500 error during permission check, unclear information about create or update).

This MR addes tests for the endpoint and refactors the endpoint.

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

Current API user may break. I do not know how to check this.

Links to related issues

https://yunity.slack.com/archives/C74JC2V26/p1663606789802519

How to test

1. Checkout branch locally
2. Run tests

Screenshots (if applicable)

Checklist

• added a test, DB Check is missing
• no unrelated changes
• asked someone for a code review
• set a "for:" label to indicate who will be affected by this change
• 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 that can be used in the release notes
• Once your MR has been merged, you are responsible to create a testing issue in the Beta Testing forum: https://foodsharing.de/?page=bezirk&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.

Release notes text in German