Daily Active User Metrics (#3735)

* agent: add StatsReporter

* Stabilize protoc

coderd/database/queries/agentstats.sql

@@ -0,0 +1,28 @@
+-- name: InsertAgentStat :one
+INSERT INTO
+	agent_stats (
+		id,
+		created_at,
+		user_id,
+		workspace_id,
+		template_id,
+		agent_id,
+		payload
+	)
+VALUES
+	($1, $2, $3, $4, $5, $6, $7) RETURNING *;
+
+-- name: GetTemplateDAUs :many
+select
+	(created_at at TIME ZONE 'UTC')::date as date,
+	count(distinct(user_id)) as amount
+from
+	agent_stats
+where template_id = $1
+group by
+	date
+order by
+	date asc;
+
+-- name: DeleteOldAgentStats :exec
+DELETE FROM AGENT_STATS WHERE created_at  < now() - interval '30 days';