Test deployment URL in integration tests

[NimJay]

Background:

• Currently, in the integration tests (configured in int.cloudbuild.yaml), we create two deployments of this Jump Start Solution (JSS):
  • a deployment using MySQL
  • a deployment using PostgreSQL

Feature request

• As part of the verification step, we should also verify that the deployment URL serves a working app.
• Just a simple HTTP GET request and confirming that the text "<title>Todo</title>" exists should suffice.
• We should minimize the amount of duplicated code when implementing this. Both simple_example and mysql should use a shared helper function.

Additional info

• We can take inspiration from this other JSS code base:

func testDeploymentUrl(t *testing.T, assert *assert.Assertions, url string) error {
	for attemptNum := 1; attemptNum <= 60; attemptNum++ {

		response, err := http.Get(url)
		if err != nil {
			t.Logf("Deployment URL HTTP request error: %s\n", err)

		} else if 200 <= response.StatusCode && response.StatusCode <= 299 { // Got some 200 response
			responseBody, err := ioutil.ReadAll(response.Body)
			if err != nil {
				return err
			}
			responseBodyString := string(responseBody)
			assert.Containsf(responseBodyString, "<title>Todo</title>", "Couldn't find text '<title>Todo</title>' in deployment's response")
			return nil

		} else { // Got a non-200 response
			t.Logf("Deployment URL responded with status code: %d.\n", response.StatusCode)
		}

		// Wait before retrying
		time.Sleep(4 * time.Second)
	}

	t.Logf("Waited too long for deployment URL.\n")
        // TODO: Consider failing
	return nil
}