[CLOUD] fix defaultRoute for app/cloud/onboarding (elastic#221029)

## Summary

The uiSettings client need to have the Kibana request to send back the
defaultRoute for a space.

### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

(cherry picked from commit 6f41f41)

Author: XavierM

x-pack/platform/plugins/shared/cloud/server/plugin.ts

@@ -249,7 +249,7 @@ export class CloudPlugin implements Plugin<CloudSetup, CloudStart> {
       },
       async (context, request, response) => {
         const { uiSettings, savedObjects } = await context.core;
-        const defaultRoute = await uiSettings.client.get<string>('defaultRoute');
+        const defaultRoute = await uiSettings.client.get<string>('defaultRoute', { request });
         const nextCandidateRoute = parseNextURL(request.url.href);
 
         const route = nextCandidateRoute === '/' ? defaultRoute : nextCandidateRoute;

x-pack/test/functional_cloud/saml.config.ts

@@ -67,6 +67,7 @@ export default async function ({ readConfigFile }: FtrConfigProviderContext) {
         '--xpack.security.authc.providers.saml.saml1.realm=saml1',
         '--xpack.security.authc.providers.basic.basic1.order=1',
         '--server.restrictInternalApis=false',
+        '--uiSettings.overrides.defaultRoute=/app/observability/landing',
       ],
     },
     uiSettings: {

x-pack/test/functional_cloud/tests/onboarding.ts

@@ -55,6 +55,15 @@ export default function ({ getService, getPageObjects }: FtrProviderContext) {
       await deleteSavedObject();
     });
 
+    it('Only redirect', async () => {
+      await browser.get(deployment.getHostPort() + `/app/cloud/onboarding`);
+      await find.byCssSelector('[data-test-subj="userMenuButton"]', 20000);
+
+      // We need to make sure that both path and hash are respected.
+      const currentURL = parse(await browser.getCurrentUrl());
+      expect(currentURL.pathname).to.eql('/app/observability/landing');
+    });
+
     it('Redirect and save token', async () => {
       await browser.get(
         deployment.getHostPort() +