feat: add Meilisearch-compatible search engine

[regisb]

The goal of this change is to introduce a search engine that is
compatible with the edx-search API but that uses Meilisearch instead of
Elasticsearch. That way, we can replace one by the other across
edx-platform by simply changing a single SEARCH_ENGINE django setting.

There are a couple of differences between Meilisearch and Elasticsearch:

1. Filterable attributes must be defined explicitly.
2. No support for datetime objects, which must be converted to
   timestamps (with an extra field to store the timezone).
3. No special characters allowed in the primary key values, such that we
   must hash course IDs before we can use them as primary key values.

Note that this PR does not introduce any breaking change. This is an
opt-in engine that anyone is free to use. There is some setup work for
every search feature: see the engine module documentation for more
information.

See the corresponding conversation here:
openedx/frontend-app-authoring#1334 (comment)

This PR replaces the corresponding one in edx-platform: openedx/edx-platform#35650

[openedx-webhooks]

Thanks for the pull request, @regisb!

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[regisb]

I will add more unit tests to improve the test coverage later. In the meantime, this PR is ready for review.

[pomegranited]

👍 Works a treat @regisb . Thank you for building this!

• I tested this on my tutor dev stack:
  • ran make compile-requirements to test the requirements & Makefile change
  • installed requirements in virtualenv and ran ./manage.py migrate to test change to manage.py
  • enabled courseware search and this new engine during launch, according to the instructions in search/meilisearch.py
  • created a new course in Studio with content
  • published the course
  • searched the course from the learning MFE and saw my published content.
• I read through the code
• I checked for accessibility issues N/A
• Includes documentation
• User-facing strings are extracted for translation

[pomegranited]

@itsjeyd @mphilbrick211 Backstage says this repo is unmaintained, but we'd really like to get this change into Sumac.
Can you help locate someone with merge rights?

CC @feanil since you touched it last 😄

[regisb]

Jill, you are faster than light.

[itsjeyd]

@pomegranited I think you did the right thing by pinging @feanil :) When a repo is unmaintained we usually need to get help from someone that's part of Axim's technical team to move forward.

[pomegranited]

@regisb

Jill, you are faster than light.

Know why? Because somebody built this amazing development and production build system that allows me test changes reliably and easily 😄

[ormsbee]

[question]: Why was this done? Why do we have these separate settings modules at all?

[pomegranited]

This was to fix an existing issue with that manage.py file -- it was referencing a non-existent file. AFAIK, you'd only use this to run a dev server locally, not for anything real.

[ormsbee]

Closing this in favor of #164, which adds more unit tests and some settings file related cleanup.