Improve performance of loading conversations

What does this MR do?

Loading conversations is quite slow since !1807 (merged) and !2134 (merged), as mentioned by some people in https://foodsharing.de/?page=bezirk&bid=734&sub=forum&tid=155152&pid=894328. I'm guessing that it is slow because the backend creates an additional query for each conversation, especially if people have many conversations. This MR is replacing that with the query from !1807 (comment 811942385) which is probably faster.

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

I'm quite sure that it works and won't break anything. I'm not sure if it actually increases performance, but it should be worth a try.

How to test

1. Checkout branch locally
2. Login as userbot
3. Open the chat menu and check that the conversations are loading
4. Open the team conversation of a store and see that the title is a link to that store
5. Open a conversation that does not belong to a store and see that the link is a title to a user profile

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
• used "state:" labels to track this MR's state until it was beta tested
• 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.