chore: add usage tracking package (#19095)

Not used in coderd yet, see stack.

Adds two new packages:
- `coderd/usage`: provides an interface for the "Collector" as well as a stub implementation for AGPL
- `enterprise/coderd/usage`: provides an interface for the "Publisher" as well as a Tallyman implementation

Relates to https://github.com/coder/internal/issues/814

coderd/database/queries/usageevents.sql

@@ -0,0 +1,86 @@
+-- name: InsertUsageEvent :exec
+-- Duplicate events are ignored intentionally to allow for multiple replicas to
+-- publish heartbeat events.
+INSERT INTO
+    usage_events (
+        id,
+        event_type,
+        event_data,
+        created_at,
+        publish_started_at,
+        published_at,
+        failure_message
+    )
+VALUES
+    (@id, @event_type, @event_data, @created_at, NULL, NULL, NULL)
+ON CONFLICT (id) DO NOTHING;
+
+-- name: SelectUsageEventsForPublishing :many
+WITH usage_events AS (
+    UPDATE
+        usage_events
+    SET
+        publish_started_at = @now::timestamptz
+    WHERE
+        id IN (
+            SELECT
+                potential_event.id
+            FROM
+                usage_events potential_event
+            WHERE
+                -- Do not publish events that have already been published or
+                -- have permanently failed to publish.
+                potential_event.published_at IS NULL
+                -- Do not publish events that are already being published by
+                -- another replica.
+                AND (
+                    potential_event.publish_started_at IS NULL
+                    -- If the event has publish_started_at set, it must be older
+                    -- than an hour ago. This is so we can retry publishing
+                    -- events where the replica exited or couldn't update the
+                    -- row.
+                    -- The parenthesis around @now::timestamptz are necessary to
+                    -- avoid sqlc from generating an extra argument.
+                    OR potential_event.publish_started_at < (@now::timestamptz) - INTERVAL '1 hour'
+                )
+                -- Do not publish events older than 30 days. Tallyman will
+                -- always permanently reject these events anyways. This is to
+                -- avoid duplicate events being billed to customers, as
+                -- Metronome will only deduplicate events within 34 days.
+                -- Also, the same parenthesis thing here as above.
+                AND potential_event.created_at > (@now::timestamptz) - INTERVAL '30 days'
+            ORDER BY potential_event.created_at ASC
+            FOR UPDATE SKIP LOCKED
+            LIMIT 100
+        )
+    RETURNING *
+)
+SELECT *
+-- Note that this selects from the CTE, not the original table. The CTE is named
+-- the same as the original table to trick sqlc into reusing the existing struct
+-- for the table.
+FROM usage_events
+-- The CTE and the reorder is required because UPDATE doesn't guarantee order.
+ORDER BY created_at ASC;
+
+-- name: UpdateUsageEventsPostPublish :exec
+UPDATE
+    usage_events
+SET
+    publish_started_at = NULL,
+    published_at = CASE WHEN input.set_published_at THEN @now::timestamptz ELSE NULL END,
+    failure_message = NULLIF(input.failure_message, '')
+FROM (
+    SELECT
+        UNNEST(@ids::text[]) AS id,
+        UNNEST(@failure_messages::text[]) AS failure_message,
+        UNNEST(@set_published_ats::boolean[]) AS set_published_at
+) input
+WHERE
+    input.id = usage_events.id
+    -- If the number of ids, failure messages, and set published ats are not the
+    -- same, do not do anything. Unfortunately you can't really throw from a
+    -- query without writing a function or doing some jank like dividing by
+    -- zero, so this is the best we can do.
+    AND cardinality(@ids::text[]) = cardinality(@failure_messages::text[])
+    AND cardinality(@ids::text[]) = cardinality(@set_published_ats::boolean[]);