test(api): enforce maxLength validation boundaries for user parameter (JhaSourav07#2059)

Fixes JhaSourav07#1428

## Description
Added comprehensive unit tests in `lib/validations.test.ts` and endpoint
integration tests in `app/api/streak/route.test.ts` to verify that the
`?user=` query handle parameter strictly enforces the 39-character
maxLength boundary condition.

## Pillar
- [x] 🛠️ Other (Bug fix, refactoring, docs, testing)

## Checklist
- [x] I have read the CONTRIBUTING.md file.
- [x] My commits follow the Conventional Commits format.
- [x] I have made sure that I have only one commit to merge in this PR.

Author: JhaSourav07

app/api/streak/route.test.ts

@@ -1,4 +1,5 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { NextRequest } from 'next/server';
 import { GET } from './route';
 
 // We only mock the two things that reach outside this process:
@@ -205,6 +206,18 @@ describe('GET /api/streak', () => {
       expect(JSON.stringify(body)).toContain('cannot exceed 39 characters');
     });
 
+    it('returns 400 Bad Request and details indicating the username cannot exceed 39 characters when using NextRequest', async () => {
+      const url = `http://localhost/api/streak?user=${'a'.repeat(40)}`;
+      const request = new NextRequest(url);
+
+      const response = await GET(request);
+
+      expect(response.status).toBe(400);
+      const body = await response.json();
+      expect(body.error).toBe('Invalid parameters');
+      expect(body.details.fieldErrors.user[0]).toMatch(/cannot exceed 39 characters/);
+    });
+
     it('returns 400 for invalid monthly badge dimensions', async () => {
       const invalidDimensionParams: Array<Record<string, string>> = [
         { width: 'abc' },

lib/validations.test.ts

@@ -99,6 +99,18 @@ describe('streakParamsSchema user validation', () => {
 
     expect(result.success).toBe(true);
   });
+
+  it('should enforce a maximum length constraint of 39 characters for the user parameter', () => {
+    const invalidUser = 'a'.repeat(40);
+    const result = streakParamsSchema.safeParse({
+      user: invalidUser,
+    });
+
+    expect(result.success).toBe(false);
+    if (!result.success) {
+      expect(result.error.issues[0]?.message).toMatch(/cannot exceed 39 characters/);
+    }
+  });
 });
 
 describe('streakParamsSchema', () => {