Remove the DJANGO_CONFIGURATION environment variable

There are a few issues with it:

* It doesn't work for the Enterprise version, because its settings module is
  not located under `cvat.settings`.

* The name `DJANGO_CONFIGURATION` suggests that it's defined by Django, but
  it isn't. It's a CVAT-specific variable. There's also a 3rd-party module
  that uses this variable (django-configurations), but with different
  semantics, which could cause confusion.

* It's just redundant to have two variables that effectively do the same thing
  (`DJANGO_CONFIGURATION` and `DJANGO_SETTINGS_MODULE`).

Besides its runtime effect, `DJANGO_CONFIGURATION` is also used in the
Dockerfile to select the packages to install. I could see that still being
useful, so replace it with a build-only variable named `CVAT_CONFIGURATION`.

Dockerfile

@@ -73,11 +73,11 @@ COPY utils/dataset_manifest/requirements.txt /tmp/utils/dataset_manifest/require
 # Exclude av from the requirements file
 RUN sed -i '/^av==/d' /tmp/utils/dataset_manifest/requirements.txt
 
-ARG DJANGO_CONFIGURATION="production"
+ARG CVAT_CONFIGURATION="production"
 
 RUN --mount=type=cache,target=/root/.cache/pip/http \
     DATUMARO_HEADLESS=1 python3 -m pip wheel --no-deps \
-    -r /tmp/cvat/requirements/${DJANGO_CONFIGURATION}.txt \
+    -r /tmp/cvat/requirements/${CVAT_CONFIGURATION}.txt \
     -w /tmp/wheelhouse
 
 FROM golang:1.20.5 AS build-smokescreen
@@ -103,8 +103,8 @@ ENV TERM=xterm \
     TZ=${TZ}
 
 ARG USER="django"
-ARG DJANGO_CONFIGURATION="production"
-ENV DJANGO_CONFIGURATION=${DJANGO_CONFIGURATION}
+ARG CVAT_CONFIGURATION="production"
+ENV DJANGO_SETTINGS_MODULE="cvat.settings.${CVAT_CONFIGURATION}"
 
 # Install necessary apt packages
 RUN apt-get update && \

Dockerfile.ci

@@ -1,6 +1,6 @@
 FROM cvat/server:local
 
-ENV DJANGO_CONFIGURATION=testing
+ENV DJANGO_SETTINGS_MODULE=cvat.settings.testing
 USER root
 
 RUN apt-get update && \
@@ -25,7 +25,7 @@ RUN apt-get update && \
 COPY cvat/requirements/ /tmp/cvat/requirements/
 COPY utils/dataset_manifest/requirements.txt /tmp/utils/dataset_manifest/requirements.txt
 
-RUN DATUMARO_HEADLESS=1 python3 -m pip install --no-cache-dir -r /tmp/cvat/requirements/${DJANGO_CONFIGURATION}.txt
+RUN DATUMARO_HEADLESS=1 python3 -m pip install --no-cache-dir -r /tmp/cvat/requirements/testing.txt
 
 COPY cvat-core ${HOME}/cvat-core
 COPY cvat-data ${HOME}/cvat-data

cvat/asgi.py

@@ -18,8 +18,7 @@ from django.core.handlers.asgi import ASGIHandler
 
 import cvat.utils.remote_debugger as debug
 
-os.environ.setdefault("DJANGO_SETTINGS_MODULE", "cvat.settings.{}" \
-    .format(os.environ.get("DJANGO_CONFIGURATION", "development")))
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "cvat.settings.development")
 
 application = get_asgi_application()
 

manage.py

@@ -8,8 +8,7 @@ import os
 import sys
 
 if __name__ == "__main__":
-    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "cvat.settings.{}" \
-        .format(os.environ.get("DJANGO_CONFIGURATION", "development")))
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "cvat.settings.development")
     try:
         from django.core.management import execute_from_command_line
     except ImportError as exc: