feat(api): load config using shared helpers

- add django settings module documentation
- use default for previously required fields

BREAKING CHANGE: The API command line interface require the
configuration file to be present. The default configuration file path is
`/etc/airtime/airtime.conf`

api/libretime_api/settings/README.md

@@ -0,0 +1,7 @@
+# Django settings
+
+The structure of the django settings module is the following:
+
+- the `__init__.py` (`libretime_api.settings`) module is the django settings entrypoint. The module contains bindings between the user configuration and the django settings. **Advanced users** may edit this file to better integrate the LibreTime API in their setup.
+- the `_internal.py` module contains application settings for django.
+- the `_schema.py` module contains the schema for the user configuration parsing and validation.

api/libretime_api/settings/__init__.py

@@ -0,0 +1,46 @@
+# pylint: disable=unused-import
+from os import getenv
+
+from ._internal import (
+    AUTH_PASSWORD_VALIDATORS,
+    AUTH_USER_MODEL,
+    DEBUG,
+    INSTALLED_APPS,
+    MIDDLEWARE,
+    REST_FRAMEWORK,
+    ROOT_URLCONF,
+    TEMPLATES,
+    TEST_RUNNER,
+    WSGI_APPLICATION,
+    setup_logger,
+)
+from ._schema import Config
+
+API_VERSION = "2.0.0"
+
+LIBRETIME_LOG_FILEPATH = getenv("LIBRETIME_LOG_FILEPATH")
+LIBRETIME_CONFIG_FILEPATH = getenv("LIBRETIME_CONFIG_FILEPATH")
+
+CONFIG = Config(filepath=LIBRETIME_CONFIG_FILEPATH)
+
+SECRET_KEY = CONFIG.general.api_key
+ALLOWED_HOSTS = ["*"]
+
+DATABASES = {
+    "default": {
+        "ENGINE": "django.db.backends.postgresql",
+        "HOST": CONFIG.database.host,
+        "PORT": CONFIG.database.port,
+        "NAME": CONFIG.database.name,
+        "USER": CONFIG.database.user,
+        "PASSWORD": CONFIG.database.password,
+    }
+}
+
+LANGUAGE_CODE = "en-us"
+TIME_ZONE = "UTC"
+USE_I18N = True
+USE_L10N = True
+USE_TZ = True
+
+LOGGING = setup_logger(LIBRETIME_LOG_FILEPATH)

api/libretime_api/settings/_internal.py

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+from os import getenv
+from typing import Optional
+
+# SECURITY WARNING: don't run with debug turned on in production!
+DEBUG = getenv("LIBRETIME_DEBUG")
+
+# Application definition
+
+INSTALLED_APPS = [
+    "libretime_api.apps.LibreTimeAPIConfig",
+    "django.contrib.auth",
+    "django.contrib.contenttypes",
+    "django.contrib.sessions",
+    "django.contrib.messages",
+    "django.contrib.staticfiles",
+    "rest_framework",
+    "django_filters",
+    "drf_spectacular",
+]
+
+MIDDLEWARE = [
+    "django.middleware.security.SecurityMiddleware",
+    "django.contrib.sessions.middleware.SessionMiddleware",
+    "django.middleware.common.CommonMiddleware",
+    "django.middleware.csrf.CsrfViewMiddleware",
+    "django.contrib.auth.middleware.AuthenticationMiddleware",
+    "django.contrib.messages.middleware.MessageMiddleware",
+    "django.middleware.clickjacking.XFrameOptionsMiddleware",
+]
+
+ROOT_URLCONF = "libretime_api.urls"
+
+TEMPLATES = [
+    {
+        "BACKEND": "django.template.backends.django.DjangoTemplates",
+        "DIRS": [],
+        "APP_DIRS": True,
+        "OPTIONS": {
+            "context_processors": [
+                "django.template.context_processors.debug",
+                "django.template.context_processors.request",
+                "django.contrib.auth.context_processors.auth",
+                "django.contrib.messages.context_processors.messages",
+            ],
+        },
+    },
+]
+
+WSGI_APPLICATION = "libretime_api.wsgi.application"
+
+# Password validation
+# https://docs.djangoproject.com/en/3.0/ref/settings/#auth-password-validators
+
+AUTH_PASSWORD_VALIDATORS = [
+    {
+        "NAME": "django.contrib.auth.password_validation.UserAttributeSimilarityValidator",
+    },
+    {
+        "NAME": "django.contrib.auth.password_validation.MinimumLengthValidator",
+    },
+    {
+        "NAME": "django.contrib.auth.password_validation.CommonPasswordValidator",
+    },
+    {
+        "NAME": "django.contrib.auth.password_validation.NumericPasswordValidator",
+    },
+]
+
+# Rest Framework settings
+# https://www.django-rest-framework.org/api-guide/settings/
+
+renderer_classes = ["rest_framework.renderers.JSONRenderer"]
+if DEBUG:
+    renderer_classes += ["rest_framework.renderers.BrowsableAPIRenderer"]
+
+REST_FRAMEWORK = {
+    "DEFAULT_RENDERER_CLASSES": renderer_classes,
+    "DEFAULT_AUTHENTICATION_CLASSES": (
+        "rest_framework.authentication.SessionAuthentication",
+        "rest_framework.authentication.BasicAuthentication",
+    ),
+    "DEFAULT_PERMISSION_CLASSES": [
+        "libretime_api.permissions.IsSystemTokenOrUser",
+    ],
+    "DEFAULT_FILTER_BACKENDS": [
+        "django_filters.rest_framework.DjangoFilterBackend",
+    ],
+    "DEFAULT_SCHEMA_CLASS": "drf_spectacular.openapi.AutoSchema",
+    "URL_FIELD_NAME": "item_url",
+}
+
+AUTH_USER_MODEL = "libretime_api.User"
+
+TEST_RUNNER = "libretime_api.tests.runners.ManagedModelTestRunner"
+
+
+# Logging
+def setup_logger(log_filepath: Optional[str]):
+    logging_handlers = {
+        "console": {
+            "level": "INFO",
+            "class": "logging.StreamHandler",
+            "formatter": "simple",
+        },
+    }
+
+    if log_filepath is not None:
+        logging_handlers["file"] = {
+            "level": "DEBUG",
+            "class": "logging.FileHandler",
+            "filename": log_filepath,
+            "formatter": "verbose",
+        }
+
+    return {
+        "version": 1,
+        "disable_existing_loggers": False,
+        "formatters": {
+            "simple": {
+                "format": "{levelname} {message}",
+                "style": "{",
+            },
+            "verbose": {
+                "format": "{asctime} {module} {levelname} {message}",
+                "style": "{",
+            },
+        },
+        "handlers": logging_handlers,
+        "loggers": {
+            "django": {
+                "handlers": logging_handlers.keys(),
+                "level": "INFO",
+                "propagate": True,
+            },
+            "libretime_api": {
+                "handlers": logging_handlers.keys(),
+                "level": "INFO",
+                "propagate": True,
+            },
+        },
+    }

api/libretime_api/settings/_schema.py

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+from libretime_shared.config import (
+    BaseConfig,
+    DatabaseConfig,
+    GeneralConfig,
+    RabbitMQConfig,
+)
+
+
+class Config(BaseConfig):
+    general: GeneralConfig
+    database: DatabaseConfig = DatabaseConfig()
+    rabbitmq: RabbitMQConfig = RabbitMQConfig()