feat: implement freemium restrictions

go/migrations/000014_network_message_usage.up.sql

@@ -0,0 +1,11 @@
+BEGIN;
+
+CREATE TABLE network_message_usage (
+  network_id    TEXT        NOT NULL REFERENCES networks(id) ON DELETE CASCADE,
+  usage_date    DATE        NOT NULL,
+  message_count INTEGER     NOT NULL DEFAULT 0,
+  updated_at    TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  PRIMARY KEY (network_id, usage_date)
+);
+
+COMMIT;