test(github route): verify 400 error for username with spaces

Author: mayank200529

app/api/streak/route.test.ts

@@ -90,6 +90,13 @@ describe('GET /api/streak', () => {
 
       expect(fetchGitHubContributions).not.toHaveBeenCalled();
     });
+    it('returns 400 when user contains spaces', async () => {
+      const response = await GET(makeRequest({ user: 'john doe' }));
+      const body = await response.json();
+
+      expect(response.status).toBe(400);
+      expect(body.details.fieldErrors.user[0]).toContain('Invalid GitHub username');
+    });
 
     it('returns 400 for invalid monthly badge dimensions', async () => {
       const invalidDimensionParams: Array<Record<string, string>> = [