AuthN: set org id for authentication request in service (#60528)

* AuthN: Replicate functionallity to get org id for request

* Authn: parse org id for the request and populate the auth request with
it

* AuthN: add simple mock for client to use in test

* AuthN: add tests to verify that authentication is called with correct
org id

* AuthN: Add ClientParams to mock

* AuthN: Fix flaky org id selection

pkg/services/authn/authn.go

@@ -42,6 +42,8 @@ type Client interface {
 }
 
 type Request struct {
+	// OrgID will be populated by authn.Service
+	OrgID       int64
 	HTTPRequest *http.Request
 }