Event-sourced applicant/subscriber/project aggregates, generalized resources

Replaces the free-string, direct-KV-mutate state model in answers.rs
with a proper event log (events/store.rs, JetStream-backed, CAS via
expected_last_subject_sequence) and three pure state machines
(aggregates/{applicant,subscriber,project}.rs). Closes a real
lost-update race in the old transition_answer (concurrent decisions on
the same item could both win, publishing contradictory events). KV
buckets become best-effort read-model projections, not the source of
truth. Content-declared transition targets are now validated at
load/reload time against the real compiled transition tables, not
accepted as arbitrary strings.

Buckets renamed to describe their content, not their relation to the
app (portal_applicants -> applicants, etc); "inquiry" folded into a
richer "project" concept.

ResourceSpec generalized beyond a single KV bucket: Kv | GiteaStarred |
GiteaOrgRepos | Url sources, with an optional jq filter (via the jaq
crate) to shape live data for the frontend. Url source is SSRF-guarded
(https-only, rejects loopback/private/link-local, real DNS resolve).

New headless question_lint binary (validates content against compiled
transition tables with no NATS/OIDC/server involved) and a one-time
backfill_events binary (dry-run by default) for migrating existing KV
data onto the new event log.

Questions get an optional `responsible` contact plus a lightweight
"report this question" action.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/events/store.rs

@@ -0,0 +1,150 @@
+//! Durable, replayable event log for the aggregate state machines in
+//! `crate::aggregates` - the source of truth `answers::Answer` KV
+//! records now only *project*. Ported from dodrenett's `lib/eventStore.ts`
+//! with two gaps closed rather than copied: dodrenett's `sequence`
+//! field was always hardcoded `0` (ordering relied entirely on
+//! JetStream's own append order anyway - here the real per-message
+//! sequence is used directly, nothing fake); dodrenett never used
+//! `Nats-Msg-Id`/CAS at all. This module uses both, via `async-nats`
+//! 0.38's native support - no new dependency.
+//!
+//! Subject scheme is `events.<aggregate_type>.<aggregate_id>`,
+//! deliberately *not* `events.<type>.<id>.<eventType>` like dodrenett -
+//! dropping the event type from the subject means
+//! `expected_last_subject_sequence` gives real optimistic concurrency
+//! across an aggregate's *entire* history, not just same-typed events.
+//! The cost: no cheap subject-wildcard query for "every `invited` event
+//! across all applicants" - nobody needs that today, and it's a filter
+//! over `load_events`'s output if it's ever needed.
+
+use serde::{Deserialize, Serialize};
+
+pub const STREAM_NAME: &str = "EVENTS";
+
+/// One durably-stored fact about an aggregate. `sequence` is filled in
+/// from JetStream's own per-message sequence number on read
+/// (`load_events`) - never trust a value baked into the payload itself.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct Event {
+    pub id: uuid::Uuid,
+    pub aggregate_type: String,
+    pub aggregate_id: String,
+    pub event_type: String,
+    pub payload: serde_json::Value,
+    pub occurred_at_ms: i64,
+    #[serde(default)]
+    pub sequence: u64,
+}
+
+fn subject(aggregate_type: &str, aggregate_id: &str) -> String {
+    format!("events.{aggregate_type}.{aggregate_id}")
+}
+
+/// Idempotent - safe to call on every boot. `max_age` deliberately left
+/// at the default (unlimited) - dodrenett's 7-day retention was an
+/// explicit dev default, not something worth inheriting for what's
+/// meant to be the durable source of truth.
+pub async fn ensure_stream(
+    js: &async_nats::jetstream::Context,
+) -> anyhow::Result<async_nats::jetstream::stream::Stream> {
+    let stream = js
+        .get_or_create_stream(async_nats::jetstream::stream::Config {
+            name: STREAM_NAME.to_string(),
+            subjects: vec!["events.>".to_string()],
+            ..Default::default()
+        })
+        .await?;
+    Ok(stream)
+}
+
+/// Appends one event. `expected_seq` set to the aggregate's last-known
+/// sequence turns this into a compare-and-swap: a concurrent caller
+/// racing against the same aggregate with a stale `expected_seq` gets
+/// `PublishError` back instead of silently winning a lost-update race
+/// (see `crate::aggregates`, `transition_answer`'s old direct
+/// KV-mutate-in-place bug this replaces). `event.id` is set as the
+/// JetStream `Nats-Msg-Id` for the stream's dedup window - only
+/// catches a genuine retry with the *same* id, not a fresh submission;
+/// callers that want real retry-dedup must pass a stable id themselves.
+/// Returns the raw `PublishError` (not wrapped in `anyhow`) so callers
+/// like `crate::aggregates::classify_publish_err` can distinguish a CAS
+/// conflict (`WrongLastSequence`) from every other failure mode.
+pub async fn append_event(
+    js: &async_nats::jetstream::Context,
+    aggregate_type: &str,
+    aggregate_id: &str,
+    event_type: &str,
+    payload: serde_json::Value,
+    occurred_at_ms: i64,
+    expected_seq: Option<u64>,
+) -> Result<async_nats::jetstream::publish::PublishAck, async_nats::jetstream::context::PublishError>
+{
+    let event = Event {
+        id: uuid::Uuid::new_v4(),
+        aggregate_type: aggregate_type.to_string(),
+        aggregate_id: aggregate_id.to_string(),
+        event_type: event_type.to_string(),
+        payload,
+        occurred_at_ms,
+        sequence: 0, // ignored on write - the server assigns the real one
+    };
+    // Every field here is a plain, always-serializable type (strings,
+    // an i64, a Uuid, a serde_json::Value) - matches `chain.rs::hash_node`'s
+    // own "json values always serialize" precedent.
+    let data = serde_json::to_vec(&event).expect("Event always serializes");
+
+    let mut publish = async_nats::jetstream::context::Publish::build()
+        .payload(data.into())
+        .message_id(event.id.to_string());
+    if let Some(seq) = expected_seq {
+        publish = publish.expected_last_subject_sequence(seq);
+    }
+
+    js.send_publish(subject(aggregate_type, aggregate_id), publish)
+        .await?
+        .await
+}
+
+/// Loads every event for one aggregate, in real JetStream append order.
+/// Uses an ephemeral pull consumer scoped to this one aggregate's
+/// subject, fetched once and torn down - same idiom dodrenett's
+/// `getEvents` used, appropriate at this scale (single-digit events per
+/// aggregate), not a durable/long-lived consumer.
+pub async fn load_events(
+    js: &async_nats::jetstream::Context,
+    aggregate_type: &str,
+    aggregate_id: &str,
+) -> anyhow::Result<Vec<Event>> {
+    use futures::TryStreamExt;
+
+    let stream = js.get_stream(STREAM_NAME).await?;
+    let subj = subject(aggregate_type, aggregate_id);
+    let consumer = stream
+        .create_consumer(async_nats::jetstream::consumer::pull::Config {
+            filter_subject: subj,
+            ..Default::default()
+        })
+        .await?;
+
+    let mut events = Vec::new();
+    let mut messages = consumer.fetch().max_messages(10_000).messages().await?;
+    while let Some(message) = messages
+        .try_next()
+        .await
+        .map_err(|e| anyhow::anyhow!("fetching messages: {e}"))?
+    {
+        let info = message.info().map_err(|e| anyhow::anyhow!("reading message info: {e}"))?;
+        let mut event: Event = serde_json::from_slice(&message.payload)?;
+        event.sequence = info.stream_sequence;
+        events.push(event);
+        message.ack().await.map_err(|e| anyhow::anyhow!("acking: {e}"))?;
+    }
+    events.sort_by_key(|e| e.sequence);
+
+    // Best-effort teardown - an ephemeral consumer left behind expires
+    // on its own (default inactive_threshold), so a delete failure here
+    // isn't worth failing the read over.
+    let _ = stream.delete_consumer(&consumer.cached_info().name).await;
+
+    Ok(events)
+}