Fix release from #1860 (hotfix #1934).

- Cron job to send weekly email report is processed multiple times. Review scheduling process to send to only one worker.
- Implement mechanism to ensure each email is sent only once to each recipient.
- Improve the way the async task is processed by creating a separate task for each organization, instead of processing all organizations in a single task.
posthog/settings.py
# Append Enterprise Edition as an app if available
try:
    from ee.apps import EnterpriseConfig
except ImportError:
    pass
else:
    HOOK_EVENTS: Dict[str, str] = {}
    INSTALLED_APPS.append("rest_hooks")
    INSTALLED_APPS.append("ee.apps.EnterpriseConfig")
    EE_AVAILABLE = True
# Use django-extensions if it exists
try:
    import django_extensions
except ImportError:
    pass
else:
    INSTALLED_APPS.append("django_extensions")
INTERNAL_IPS = ["127.0.0.1", "172.18.0.1"]  # Docker IP
CORS_ORIGIN_ALLOW_ALL = True
ROOT_URLCONF = "posthog.urls"
TEMPLATES = [
    {
        "BACKEND": "django.template.backends.django.DjangoTemplates",
        "DIRS": ["frontend/dist", "posthog/templates"],
        "APP_DIRS": True,
        "OPTIONS": {
            "context_processors": [
                "django.template.context_processors.debug",
                "django.template.context_processors.request",
                "django.contrib.auth.context_processors.auth",