[MM-29845] Add a new handler to allow authentication via CWS API Key (#16319)

* Add a new handler to allow authentication via CWS API Key

* Make error better

* Add tests and cases for new handler functions

* Move some code around

* Add test for GetCloudSession function

* unset the env after test completion

* Remove white space

* Change Info to Warn

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/client4.go

@@ -31,6 +31,7 @@ const (
 	HEADER_CSRF_TOKEN         = "X-CSRF-Token"
 	HEADER_BEARER             = "BEARER"
 	HEADER_AUTH               = "Authorization"
+	HEADER_CLOUD_TOKEN        = "X-Cloud-Token"
 	HEADER_REQUESTED_WITH     = "X-Requested-With"
 	HEADER_REQUESTED_WITH_XML = "XMLHttpRequest"
 	STATUS                    = "status"