Draft: Add feature to change password

Closes #581

What does this MR do?

Allows users to change their own login password. There is a small form in the profile settings and a new API endpoint.

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

Quite sure. This doesn't alter any existing code.

Links to related issues

How to test

1. Checkout branch locally
2. Login as foodsaver
3. Open your profile settings
4. Type in the old password (default is "user") and a new one
5. Submit, logout and test your new password

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.

Closes #581