feat: add Meilisearch-compatible search engine

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)

requirements/base.in

@@ -15,3 +15,4 @@ Django                       # Web application framework
 elasticsearch>=7.8.0,<8.0.0
 edx-toggles
 event-tracking
+meilisearch

requirements/base.txt

@@ -6,18 +6,26 @@
 #
 amqp==5.2.0
     # via kombu
+annotated-types==0.7.0
+    # via pydantic
 asgiref==3.8.1
     # via django
 attrs==23.2.0
     # via openedx-events
 billiard==4.2.0
     # via celery
+camel-converter[pydantic]==4.0.1
+    # via meilisearch
 celery==5.4.0
     # via event-tracking
 certifi==2024.7.4
-    # via elasticsearch
+    # via
+    #   elasticsearch
+    #   requests
 cffi==1.16.0
     # via pynacl
+charset-normalizer==3.4.0
+    # via requests
 click==8.1.7
     # via
     #   celery
@@ -77,12 +85,16 @@ event-tracking==2.4.0
     #   -r requirements/base.in
 fastavro==1.9.5
     # via openedx-events
+idna==3.10
+    # via requests
 jinja2==3.1.4
     # via code-annotations
 kombu==5.3.7
     # via celery
 markupsafe==2.1.5
     # via jinja2
+meilisearch==0.31.5
+    # via -r requirements/base.in
 newrelic==9.12.0
     # via edx-django-utils
 openedx-events==9.11.0
@@ -95,6 +107,10 @@ psutil==6.0.0
     # via edx-django-utils
 pycparser==2.22
     # via cffi
+pydantic==2.9.2
+    # via camel-converter
+pydantic-core==2.23.4
+    # via pydantic
 pymongo==3.13.0
     # via
     #   edx-opaque-keys
@@ -109,6 +125,8 @@ pytz==2024.1
     # via event-tracking
 pyyaml==6.0.1
     # via code-annotations
+requests==2.32.3
+    # via meilisearch
 six==1.16.0
     # via
     #   edx-ccx-keys
@@ -124,11 +142,16 @@ stevedore==5.2.0
 text-unidecode==1.3
     # via python-slugify
 typing-extensions==4.12.2
-    # via edx-opaque-keys
+    # via
+    #   edx-opaque-keys
+    #   pydantic
+    #   pydantic-core
 tzdata==2024.1
     # via celery
 urllib3==1.26.19
-    # via elasticsearch
+    # via
+    #   elasticsearch
+    #   requests
 vine==5.1.0
     # via
     #   amqp

requirements/dev.txt

@@ -9,6 +9,11 @@ amqp==5.2.0
     #   -r requirements/quality.txt
     #   -r requirements/testing.txt
     #   kombu
+annotated-types==0.7.0
+    # via
+    #   -r requirements/quality.txt
+    #   -r requirements/testing.txt
+    #   pydantic
 asgiref==3.8.1
     # via
     #   -r requirements/quality.txt
@@ -37,6 +42,11 @@ cachetools==5.4.0
     # via
     #   -r requirements/ci.txt
     #   tox
+camel-converter[pydantic]==4.0.1
+    # via
+    #   -r requirements/quality.txt
+    #   -r requirements/testing.txt
+    #   meilisearch
 celery==5.4.0
     # via
     #   -r requirements/quality.txt
@@ -47,6 +57,7 @@ certifi==2024.7.4
     #   -r requirements/quality.txt
     #   -r requirements/testing.txt
     #   elasticsearch
+    #   requests
 cffi==1.16.0
     # via
     #   -r requirements/quality.txt
@@ -56,6 +67,11 @@ chardet==5.2.0
     # via
     #   -r requirements/ci.txt
     #   tox
+charset-normalizer==3.4.0
+    # via
+    #   -r requirements/quality.txt
+    #   -r requirements/testing.txt
+    #   requests
 click==8.1.7
     # via
     #   -r requirements/pip-tools.txt
@@ -185,6 +201,11 @@ filelock==3.15.4
     #   -r requirements/ci.txt
     #   tox
     #   virtualenv
+idna==3.10
+    # via
+    #   -r requirements/quality.txt
+    #   -r requirements/testing.txt
+    #   requests
 iniconfig==2.0.0
     # via
     #   -r requirements/quality.txt
@@ -213,6 +234,10 @@ mccabe==0.7.0
     # via
     #   -r requirements/quality.txt
     #   pylint
+meilisearch==0.31.5
+    # via
+    #   -r requirements/quality.txt
+    #   -r requirements/testing.txt
 mock==5.1.0
     # via
     #   -r requirements/quality.txt
@@ -275,6 +300,16 @@ pycparser==2.22
     #   -r requirements/quality.txt
     #   -r requirements/testing.txt
     #   cffi
+pydantic==2.9.2
+    # via
+    #   -r requirements/quality.txt
+    #   -r requirements/testing.txt
+    #   camel-converter
+pydantic-core==2.23.4
+    # via
+    #   -r requirements/quality.txt
+    #   -r requirements/testing.txt
+    #   pydantic
 pylint==3.2.6
     # via
     #   -r requirements/quality.txt
@@ -344,6 +379,11 @@ pyyaml==6.0.1
     #   -r requirements/quality.txt
     #   -r requirements/testing.txt
     #   code-annotations
+requests==2.32.3
+    # via
+    #   -r requirements/quality.txt
+    #   -r requirements/testing.txt
+    #   meilisearch
 six==1.16.0
     # via
     #   -r requirements/quality.txt
@@ -380,6 +420,8 @@ typing-extensions==4.12.2
     #   -r requirements/quality.txt
     #   -r requirements/testing.txt
     #   edx-opaque-keys
+    #   pydantic
+    #   pydantic-core
 tzdata==2024.1
     # via
     #   -r requirements/quality.txt
@@ -390,6 +432,7 @@ urllib3==1.26.19
     #   -r requirements/quality.txt
     #   -r requirements/testing.txt
     #   elasticsearch
+    #   requests
 vine==5.1.0
     # via
     #   -r requirements/quality.txt

requirements/quality.txt

@@ -8,6 +8,10 @@ amqp==5.2.0
     # via
     #   -r requirements/testing.txt
     #   kombu
+annotated-types==0.7.0
+    # via
+    #   -r requirements/testing.txt
+    #   pydantic
 asgiref==3.8.1
     # via
     #   -r requirements/testing.txt
@@ -24,6 +28,10 @@ billiard==4.2.0
     # via
     #   -r requirements/testing.txt
     #   celery
+camel-converter[pydantic]==4.0.1
+    # via
+    #   -r requirements/testing.txt
+    #   meilisearch
 celery==5.4.0
     # via
     #   -r requirements/testing.txt
@@ -32,10 +40,15 @@ certifi==2024.7.4
     # via
     #   -r requirements/testing.txt
     #   elasticsearch
+    #   requests
 cffi==1.16.0
     # via
     #   -r requirements/testing.txt
     #   pynacl
+charset-normalizer==3.4.0
+    # via
+    #   -r requirements/testing.txt
+    #   requests
 click==8.1.7
     # via
     #   -r requirements/testing.txt
@@ -130,6 +143,10 @@ fastavro==1.9.5
     # via
     #   -r requirements/testing.txt
     #   openedx-events
+idna==3.10
+    # via
+    #   -r requirements/testing.txt
+    #   requests
 iniconfig==2.0.0
     # via
     #   -r requirements/testing.txt
@@ -150,6 +167,8 @@ markupsafe==2.1.5
     #   jinja2
 mccabe==0.7.0
     # via pylint
+meilisearch==0.31.5
+    # via -r requirements/testing.txt
 mock==5.1.0
     # via -r requirements/testing.txt
 newrelic==9.12.0
@@ -188,6 +207,14 @@ pycparser==2.22
     # via
     #   -r requirements/testing.txt
     #   cffi
+pydantic==2.9.2
+    # via
+    #   -r requirements/testing.txt
+    #   camel-converter
+pydantic-core==2.23.4
+    # via
+    #   -r requirements/testing.txt
+    #   pydantic
 pylint==3.2.6
     # via
     #   edx-lint
@@ -233,6 +260,10 @@ pyyaml==6.0.1
     # via
     #   -r requirements/testing.txt
     #   code-annotations
+requests==2.32.3
+    # via
+    #   -r requirements/testing.txt
+    #   meilisearch
 six==1.16.0
     # via
     #   -r requirements/testing.txt
@@ -260,6 +291,8 @@ typing-extensions==4.12.2
     # via
     #   -r requirements/testing.txt
     #   edx-opaque-keys
+    #   pydantic
+    #   pydantic-core
 tzdata==2024.1
     # via
     #   -r requirements/testing.txt
@@ -268,6 +301,7 @@ urllib3==1.26.19
     # via
     #   -r requirements/testing.txt
     #   elasticsearch
+    #   requests
 vine==5.1.0
     # via
     #   -r requirements/testing.txt