Add timestamp to mods for some resumability

migrations/20210729031521_add_downloaded_at_to_files.sql

@@ -1,6 +1,6 @@
 ALTER TABLE "files" ADD COLUMN "downloaded_at" TIMESTAMP(3);
 
-/* Backfill existing columns the created_at timestamps.
+/* Backfill existing columns using the created_at timestamps.
  *
  * This is approximate since usually the file was downloaded shortly after the record was created.
  * I mostly only care whether it is null or not null. All existing files need non-null values.

migrations/20210729040241_add_last_updated_files_at_to_mods.sql

@@ -0,0 +1,8 @@
+ALTER TABLE "mods" ADD COLUMN "last_updated_files_at" TIMESTAMP(3);
+
+/* Backfill existing columns using the updated_at timestamps.
+ *
+ * This is approximate since usually the files are downloaded shortly after the mod record was created.
+ * I mostly only care whether it is null or not null. Most existing mods need non-null values.
+ */
+UPDATE "mods" SET "last_updated_files_at" = "updated_at";