* Check whether mfa is required for an app session through the correct cluster.
* Add clusterId param for isMfaRequired check in the web api.
* Fix connecting to leaf app directly with MFA.
* Add integration test.
* Add integration test.
* Remove redundant lib.SetInsecureDevMode calls when using testserver.SetupTrustedCluster.
* Reuse new test helpers.
* Focus fix down for apps.