Add account self-delete and subscription lifecycle sync (#34) (#39)

## Summary
- Closes [#34](#34)
- Companion for [chat_web_app#75](ai_ml_operations/chat_web_app#75) (portal cancel/change local sync)
- Soft-delete `DELETE /api/user/` for the authenticated user only: `deleted=True`, `is_active=False`, hide conversations, blacklist outstanding refresh tokens; staff self-delete rejected
- Stripe `customer.subscription.updated` / `deleted` webhooks sync plan status, `cancel_at_period_end`, and `current_period_end`; checkout assigns plan from `metadata.plan_slug`
- **UserAuthEvent audit**: `account_deleted`, `subscription_started` (first active plan), `subscription_updated` (plan/status/cancel changes) — visible on user admin
- Document FE contract in README (endpoint, response, post-delete logout)

## Test plan
- [ ] `uv run python manage.py test chat_backend.tests.test_views_users.CustomUserSelfDeleteTestCase finance.tests`
- [ ] Authenticated `DELETE /api/user/` soft-deletes self, hides conversations, blocks re-login, writes `account_deleted` auth event
- [ ] Checkout / Backer assign writes `subscription_started`; portal cancel/change writes `subscription_updated`
- [ ] Anonymous / staff self-delete rejected; body cannot target another user
- [ ] After portal cancel, webhook sets `cancel_at_period_end` / `canceled` on `GET /finance/subscription/`Reviewed-on: #39

llm_be/finance/services/webhooks.py

@@ -10,13 +10,68 @@ from django.contrib.auth import get_user_model
 from django.db import transaction
 from django.utils import timezone
 
-from finance.models import Invoice, Payment
-from finance.services.plans import assign_founders_from_stripe
+from finance.models import Invoice, Payment, UserSubscription
+from finance.services.plans import (
+    assign_plan_from_stripe,
+    get_or_create_user_subscription,
+    log_subscription_auth_event,
+    resolve_plan_from_stripe_price,
+)
 
 logger = logging.getLogger(__name__)
 User = get_user_model()
 
 
+def _stripe_status_to_local(stripe_status: str | None) -> str:
+    mapping = {
+        "active": UserSubscription.Status.ACTIVE,
+        "trialing": UserSubscription.Status.ACTIVE,
+        "past_due": UserSubscription.Status.PAST_DUE,
+        "unpaid": UserSubscription.Status.PAST_DUE,
+        "canceled": UserSubscription.Status.CANCELED,
+        "incomplete_expired": UserSubscription.Status.CANCELED,
+    }
+    return mapping.get((stripe_status or "").lower(), UserSubscription.Status.NONE)
+
+
+def _plan_slug_from_subscription(subscription: dict[str, Any]) -> str | None:
+    metadata = subscription.get("metadata") or {}
+    if metadata.get("plan_slug"):
+        return metadata.get("plan_slug")
+    items = (subscription.get("items") or {}).get("data") or []
+    if not items:
+        return None
+    price = (items[0] or {}).get("price") or {}
+    price_id = price.get("id") if isinstance(price, dict) else None
+    plan = resolve_plan_from_stripe_price(price_id)
+    return plan.slug if plan else None
+
+
+def _user_from_subscription(subscription: dict[str, Any]):
+    metadata = subscription.get("metadata") or {}
+    user = _user_from_metadata(metadata)
+    if user is not None:
+        return user
+    sub_id = subscription.get("id")
+    if sub_id:
+        existing = (
+            Invoice.objects.filter(stripe_subscription_id=sub_id)
+            .select_related("user")
+            .order_by("-created")
+            .first()
+        )
+        if existing:
+            return existing.user
+        local_sub = (
+            UserSubscription.objects.filter(stripe_subscription_id=sub_id)
+            .select_related("user")
+            .first()
+        )
+        if local_sub:
+            return local_sub.user
+    return None
+
+
 def _ts_to_dt(value: int | None):
     if not value:
         return None
@@ -213,8 +268,9 @@ def handle_checkout_session_completed(session: dict[str, Any]) -> Invoice | None
             paid_at=timezone.now(),
         )
     if session.get("payment_status") == "paid" or session.get("subscription"):
-        assign_founders_from_stripe(
+        assign_plan_from_stripe(
             user,
+            plan_slug=metadata.get("plan_slug"),
             stripe_subscription_id=session.get("subscription") or "",
         )
     return invoice
@@ -276,8 +332,9 @@ def handle_invoice_paid(stripe_invoice: dict[str, Any]) -> Invoice | None:
             stripe_charge_id=charge if isinstance(charge, str) else None,
             paid_at=paid_at,
         )
-    assign_founders_from_stripe(
+    assign_plan_from_stripe(
         user,
+        plan_slug=metadata.get("plan_slug"),
         stripe_subscription_id=stripe_invoice.get("subscription") or "",
     )
     return invoice
@@ -326,6 +383,68 @@ def handle_invoice_payment_failed(stripe_invoice: dict[str, Any]) -> Invoice | N
     return invoice
 
 
+def handle_customer_subscription_updated(subscription: dict[str, Any]):
+    """Sync local UserSubscription after portal plan change / cancel schedule."""
+    user = _user_from_subscription(subscription)
+    if user is None:
+        logger.error(
+            "customer.subscription.updated: cannot resolve user for %s",
+            subscription.get("id"),
+        )
+        return None
+
+    local_status = _stripe_status_to_local(subscription.get("status"))
+    if subscription.get("cancel_at_period_end") and local_status == (
+        UserSubscription.Status.ACTIVE
+    ):
+        # Still active until period end; keep ACTIVE and surface cancel flag.
+        pass
+
+    return assign_plan_from_stripe(
+        user,
+        plan_slug=_plan_slug_from_subscription(subscription),
+        stripe_subscription_id=subscription.get("id") or "",
+        status=local_status or UserSubscription.Status.ACTIVE,
+        cancel_at_period_end=bool(subscription.get("cancel_at_period_end")),
+        current_period_end=_ts_to_dt(subscription.get("current_period_end")),
+        keep_existing_plan_if_unknown=True,
+    )
+
+
+def handle_customer_subscription_deleted(subscription: dict[str, Any]):
+    """Mark local subscription canceled when Stripe subscription ends."""
+    user = _user_from_subscription(subscription)
+    if user is None:
+        logger.error(
+            "customer.subscription.deleted: cannot resolve user for %s",
+            subscription.get("id"),
+        )
+        return None
+
+    sub = get_or_create_user_subscription(user)
+    prev_status = sub.status
+    sub.status = UserSubscription.Status.CANCELED
+    sub.cancel_at_period_end = False
+    sub.current_period_end = _ts_to_dt(subscription.get("current_period_end"))
+    if subscription.get("id"):
+        sub.stripe_subscription_id = subscription["id"]
+    # Preserve plan so UI can show what ended; source stays stripe.
+    if sub.source == UserSubscription.Source.NONE:
+        sub.source = UserSubscription.Source.STRIPE
+    sub.save()
+    if prev_status != UserSubscription.Status.CANCELED:
+        log_subscription_auth_event(
+            user,
+            started=False,
+            detail=(
+                f"plan={sub.plan.slug if sub.plan_id else 'none'} "
+                f"source={sub.source} status={sub.status} "
+                f"stripe_subscription_id={sub.stripe_subscription_id}"
+            ),
+        )
+    return sub
+
+
 def dispatch_stripe_event(event: dict[str, Any]):
     """Route a verified Stripe event to the appropriate handler."""
     event_type = event.get("type")
@@ -337,6 +456,10 @@ def dispatch_stripe_event(event: dict[str, Any]):
         return handle_invoice_paid(data_object)
     if event_type == "invoice.payment_failed":
         return handle_invoice_payment_failed(data_object)
+    if event_type == "customer.subscription.updated":
+        return handle_customer_subscription_updated(data_object)
+    if event_type == "customer.subscription.deleted":
+        return handle_customer_subscription_deleted(data_object)
 
     logger.info("Ignoring unhandled Stripe event type: %s", event_type)
     return None