feat(subscriptions): bring subscriptions to the free tier

[vdekrijger]

Problem

Insight & dashboard subscriptions were a hard paid feature — free-tier orgs were blocked entirely (a PremiumFeaturePermission gate on the viewsets and a full-page PayGateMini on the UI). That's a missed adoption/stickiness opportunity: free users can't experience the feature before deciding to upgrade.

Changes

Make subscriptions freemium, mirroring how alerts already work: free orgs get a small allowance, then hit the existing paywall.

• Free tier gets 5 subscriptions (team-wide, non-deleted), the limit read live from the alert free-tier constant (AlertConfiguration.ALERTS_ALLOWED_ON_FREE_TIER) so the two never drift.
• Paid tier is unlimited (the SUBSCRIPTIONS entitlement carries no numeric limit → unlimited), unchanged.
• Viewing / editing / disabling / deleting existing subscriptions is never gated — even at/over the limit. The paywall appears only when a free user at the limit tries to add an additional subscription.

Backend:

• Subscription.check_subscription_limit() — a near-exact mirror of AlertConfiguration.check_alert_limit (reads the billing entitlement limit, falls back to the free-tier constant). Counts deleted=False rows.
• Enforced in SubscriptionSerializer.validate() on POST only (edits via PATCH are never blocked).
• Removed PremiumFeaturePermission from SubscriptionViewSet and SubscriptionDeliveryViewSet so free orgs can list/read.

Frontend:

• subscriptionCountLogic — lazily loads the team-wide count via the generated API (limit=1, reads count).
• The paywall collapses to a single chokepoint: EditSubscription create mode (id === 'new'). A FreeTierCreateGate shows the form while under the limit and the existing PayGateMini upsell at/over it (isFreeTierCreateAtLimit). Fail-open while the count is loading — the backend is the hard guarantee.
• Removed the three wholesale PayGateMini wrappers (list scene, single scene, subscribe modal) and unhid the insight side-panel "Subscription" menu item for free users.

No DB migration, no schema/serializer-field changes (so no generated-type churn).

Screenshots (Storybook, real components)

Free, under limit	Free, at limit
New Subscription form renders	PayGateMini upsell ("Insight & dashboard subscriptions — Upgrade to use this feature", View plans / Learn more)

(Editing an existing subscription and managing the list render normally for free orgs — no wholesale paywall.)

How did you test this code?

This PR was authored by an agent (see Agent context). No manual click-testing is claimed — below are the automated tests actually run, all green:

• Backend integration (ee/api/test/test_subscription.py, posthog/models/test/test_subscription_model.py) — real requests through the full Django stack against Postgres: free org creates 5 → 6th returns 400 under the subscription key; PATCH at the limit returns 200; soft-delete frees a slot; paid org unlimited; free orgs can list/read; check_subscription_limit parameterized over free/paid/numeric-limit/zero/soft-deleted. 152 passed.
• Frontend unit (jest, src/lib/components/Subscriptions, src/scenes/subscriptions) — isFreeTierCreateAtLimit boundary cases, count-loader (count field + limit=1 invariant + fallback), gate wiring. 63 passed.
• Live browser e2e (playwright/e2e/subscriptions-freemium.spec.ts) — drove the real frontend against a running stack:

Running 2 tests using 1 worker
  ✓ subscriptions freemium gate › free org under the limit can open the create form
  ✓ subscriptions freemium gate › free org at the limit sees the upgrade paywall instead of the create form
  2 passed (29.0s)

The e2e mocks the org entitlement + team subscription count (the gate is a pure frontend decision: !hasSubscriptionsFeature && count >= FREE_LIMIT); the hard backend limit is covered by the backend tests.

Publish to changelog?

Yes — "Subscriptions are now available on the free tier (up to 5, then upgrade for unlimited)."

Docs update

Subscriptions docs may want a note that the free tier includes up to 5 subscriptions.

🤖 Agent context

Authored with Claude Code via a proof-driven-dev workflow (spec → testable criteria matrix → plan → TDD task-by-task with per-task spec + code-quality review → verification report + rerunnable scripts/verify-subscriptions-free-tier.sh). Hardened with a local multi-reviewer pass; the one substantive finding (a tautological frontend constant test) was fixed by extracting the gate decision into the tested isFreeTierCreateAtLimit predicate.

Key decisions:

• Mirror alerts rather than invent a new mechanism. Alerts already implement "N free, then paywall"; subscriptions now reuse that exact shape (constant fallback + entitlement limit), including reading the alert free-tier constant live so the two stay in lockstep. No billing-service change.
• Gate the create entry, not the whole UI. Edits/views must stay open even at the limit, so the paywall moved from the wholesale wrappers to EditSubscription create mode only — which also covers every create entry point in one place.
• Fail-open on the frontend. If the count is still loading, the form shows; the backend POST check is the authoritative limit.

Agent-authored; requires human review. Verified via the automated tests listed above (including a live browser e2e run against a local stack).

[vdekrijger]

Superseded by a 2-PR Graphite stack on the main repo: #59624 (freemium subscriptions) and #59625 (AI-summary credit gate, stacked). Moved off the fork to PostHog/posthog.