Isolate all TS stuff in hello package

hello/test/hello-world-ts.test.ts

@@ -0,0 +1,15 @@
+process.env.CDS_TYPESCRIPT = 'true';
+import * as cds from '@sap/cds';
+
+//@ts-ignore
+const {GET} = cds.test.in(__dirname,'..').run('serve', 'world.cds');
+
+describe('Hello world!', () => {
+    afterAll(() => { delete process.env.CDS_TYPESCRIPT; });
+
+    it('should say hello with class impl from a typescript file', async () => {
+        const {data} = await GET`/say/hello(to='world')`
+        expect(data.value).toMatch(/Hello world.*typescript.*/i)
+    })
+
+})

hello/test/test.http

@@ -0,0 +1 @@
+GET http://localhost:4004/say/hello(to='world')