Add 'parent' link check in collections test

Add test to check for 'parent' link in collections response

Author: VincentKuehn

api/__tests__/api.test.js

@@ -86,6 +86,7 @@ describe('STAC API Core Endpoints', () => {
     const rels = response.body.links.map(l => l.rel);
     expect(rels).toContain('self');
     expect(rels).toContain('root');
+	expect(rels).toContain('parent');	  
   });
   });