add tag migrations and update send / saveEvent

db/postgresql/migrations/07_add_tag/migration.sql

@@ -0,0 +1,5 @@
+-- AlterTable
+ALTER TABLE "website_event" ADD COLUMN     "tag" VARCHAR(50);
+
+-- CreateIndex
+CREATE INDEX "website_event_website_id_created_at_tag_idx" ON "website_event"("website_id", "created_at", "tag");