Emeis

Bump to latest Django LTS and lift other dependencies while giving some slack on the version requirements in `setup.py` so it won't be too hard to bump to this release.

Feature
* **core** Rename the basemodel's `meta` field to `metainfo` in order to respect reserved words of [django-restframework-json-api](https://github.com/django-json-api/django-rest-framework-json-api/blob/main/CHANGELOG.md#430---2021-12-10) ([`be444a6`](https://github.com/projectcaluma/emeis/pull/298/commits/be444a622b05139df041b2530018672cb95dad91))

Breaking
* Rename basemodel's `meta` field to `metainfo`

Bugfix / Refactor


* refactor: drop django-tree-queries & implement array-based tree functions
This brings a massive performance improvement compared to 2.1.0
([`30ed6c43f293c5e45bbacbd735580142fa567e78 `](https://github.com/projectcaluma/emeis/commit/30ed6c43f293c5e45bbacbd735580142fa567e78 ))

Feature

* feat(models): (re)introduce some convenience methods for working with scope trees

The Django-MPTT module provided some useful methods that are not available anymore
with django-tree-queries. Luckily, it&39;s relatively easy to provide workarounds.

Note that they might not have the same performance/efficiency as the
MPTT variants, and could possibly be built in a better way. However,
let&39;s keep it to the motto &34;first make it right, then fast, then
pretty&34; ([`e2f38f1`](https://github.com/projectcaluma/emeis/commit/e2f38f13f8a69e5e4ac74611e0ceed50e5d81f50))

Refactor (Breaking change!)

* refactor: drop django-mptt in favour of django-tree-queries

Django-Tree-Queries works with recursive CTEs (common table expressions) to deal
with hierarchical relationships, generally achieving the same result, but without
the `right`, `left` and `tree_id` fields.

Django-MPTT has been unmaintained for several years, and we&39;re suspecting some
subtle bugs in it that we can&39;t really reproduce or verify right now. Anyway it&39;s
a good time to get rid of it.

Note: Some old migrations needed to be changed, as we cannot refer to
MPTT fields anymore. They were essentially regular foreign keys however,
so this won&39;t break the database.

BREAKING! This breaks if Emeis is used as a Django app directly, and depends on
any of the MPTT API / features. ([`61a30e0`](https://github.com/projectcaluma/emeis/commit/61a30e018736c77c0b815f5c4315f7773c824804))

Fix

* fix(setup): further loosen base requirements ([`8b21078`](https://github.com/projectcaluma/emeis/commit/8b21078f9273203a16da6077cf8efddad03fd217))

Fix

* fix(setup): loosen requirements ([`310d841`](https://github.com/projectcaluma/emeis/commit/310d841c4ed224fc29c9ef22b7a69eb5cfb46e06))