Buildings API endpoints with partial info

[JustBeYou]

What does it fix?

Listing and searching buildings return only part of the details.
The client loads full info on request. (see BuildingDetailsFragment)

Closes #573

How has it been tested?

Added unit tests. Manual testing on the frontend, the screenshots below.

[vercel]

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[JustBeYou]

Sorry for spamming with commits, but black is failing even if on my local machine everything is all right.

(‿ˠ‿) ❯ ❯) black --line-length 80 --target-version py37 --exclude migrations --check ./api
All done! ✨ 🍰 ✨
33 files would be left unchanged.

[tudoramariei]

Make sure you have the right version of Black on your PC
Right now, it's testing with black==20.8b1

[JustBeYou]

Thank you. Should be fine now.

[tudoramariei]

@JustBeYou we merged some PRs and caused a few conflicts in your PR; we can merge the PR as soon as they're solved :)

[JustBeYou]

@tudoramariei good to go 😃

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