Add 008-rsvp feature spec and design artifacts

Spec, research decisions, implementation plan, data model,
API contract, and task breakdown for the RSVP feature.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

specs/008-rsvp/data-model.md

@@ -0,0 +1,93 @@
+# Data Model: RSVP to an Event (008)
+
+**Date**: 2026-03-06
+
+## Entities
+
+### Rsvp (NEW)
+
+| Field      | Type           | Required | Constraints                    | Notes                              |
+|------------|----------------|----------|--------------------------------|------------------------------------|
+| id         | Long           | yes      | BIGSERIAL, PK                  | Internal only, never exposed       |
+| rsvpToken  | RsvpToken      | yes      | UNIQUE, NOT NULL               | Server-generated UUID, returned to client |
+| eventId    | Long           | yes      | FK -> events.id, NOT NULL      | Which event this RSVP belongs to   |
+| name       | String         | yes      | 1-100 chars, NOT NULL          | Guest's display name               |
+
+**Notes**:
+- No `attending` boolean — existence of an entry implies attendance (per spec).
+- No `createdAt` — not required by the spec. Can be added later if needed (e.g. for guest list sorting in 009).
+- Duplicates from different devices or cleared localStorage are accepted (privacy trade-off).
+
+### Token Value Objects (NEW)
+
+| Record           | Field | Type | Notes                                         |
+|------------------|-------|------|-----------------------------------------------|
+| `EventToken`     | value | UUID | Immutable, non-null. Java record wrapping UUID |
+| `OrganizerToken` | value | UUID | Immutable, non-null. Java record wrapping UUID |
+| `RsvpToken`      | value | UUID | Immutable, non-null. Java record wrapping UUID |
+
+**Purpose**: Type-safe wrappers preventing mix-ups between the three token types at compile time. All generated server-side via `UUID.randomUUID()`. JPA entities continue to use raw `UUID` columns — mapping happens in the persistence adapters.
+
+### Event (MODIFIED — token fields change type)
+
+The Event domain model's `eventToken` and `organizerToken` fields change from raw `UUID` to their typed record wrappers. No database schema change — the JPA entity keeps raw `UUID` columns.
+
+| Field           | Old Type | New Type         |
+|-----------------|----------|------------------|
+| eventToken      | UUID     | EventToken       |
+| organizerToken  | UUID     | OrganizerToken   |
+
+The `attendeeCount` was already added to the API response in 007-view-event — it now gets populated from a count query instead of returning 0.
+
+### StoredEvent (frontend localStorage — modified)
+
+| Field          | Type   | Required | Notes                              |
+|----------------|--------|----------|------------------------------------|
+| eventToken     | string | yes      | Existing                           |
+| organizerToken | string | no       | Existing (organizer flow)          |
+| title          | string | yes      | Existing                           |
+| dateTime       | string | yes      | Existing                           |
+| expiryDate     | string | yes      | Existing                           |
+| rsvpToken      | string | no       | **NEW** — set after RSVP submission |
+| rsvpName       | string | no       | **NEW** — guest's submitted name    |
+
+## Validation Rules
+
+- `name`: required, 1-100 characters, trimmed. Blank or whitespace-only is rejected.
+- `rsvpToken`: server-generated, never from client input on create.
+- `eventId`: must reference an existing, non-expired event.
+
+## Relationships
+
+```
+Event 1 <---- * Rsvp
+  |               |
+  eventToken      rsvpToken (unique)
+  (public)        (returned to client)
+```
+
+## Type Mapping (full stack)
+
+| Concept      | Java              | PostgreSQL    | OpenAPI             | TypeScript |
+|--------------|-------------------|---------------|---------------------|------------|
+| RSVP ID      | `Long`            | `bigserial`   | N/A (not exposed)   | N/A        |
+| RSVP Token   | `RsvpToken`       | `uuid`        | `string` `uuid`     | `string`   |
+| Event FK     | `Long`            | `bigint`      | N/A (path param)    | N/A        |
+| Guest name   | `String`          | `varchar(100)`| `string`            | `string`   |
+| Attendee cnt | `long`            | `count(*)`    | `integer`           | `number`   |
+
+## Database Migration
+
+New Liquibase changeset `003-create-rsvps-table.xml`:
+
+```sql
+CREATE TABLE rsvps (
+    id          BIGSERIAL PRIMARY KEY,
+    rsvp_token  UUID NOT NULL UNIQUE,
+    event_id    BIGINT NOT NULL REFERENCES events(id),
+    name        VARCHAR(100) NOT NULL
+);
+
+CREATE INDEX idx_rsvps_event_id ON rsvps(event_id);
+CREATE INDEX idx_rsvps_rsvp_token ON rsvps(rsvp_token);
+```