factor out tuple logic into from-tuple.ts

packages/backend/test/unit/misc/from-tuple.ts

@@ -0,0 +1,13 @@
+import { fromTuple } from '@/misc/from-tuple.js';
+
+describe(fromTuple, () => {
+	it('should return value when value is not an array', () => {
+		const value = fromTuple('abc');
+		expect(value).toBe('abc');
+	});
+
+	it('should return first element when value is an array', () => {
+		const value = fromTuple(['abc']);
+		expect(value).toBe('abc');
+	});
+});