通知部分は残す

Co-Authored-By: rinsuki <428rinsuki+contact.github@gmail.com>

packages/backend/src/misc/is-not-null.ts

@@ -0,0 +1,5 @@
+// we are using {} as "any non-nullish value" as expected
+// eslint-disable-next-line @typescript-eslint/ban-types
+export function isNotNull<T extends {}>(input: T | undefined | null): input is T {
+	return input != null;
+}