[MM-43917] Cloud Freemium limits API: messages/posts (#20152)

* WIP - Add api and app funcs

* Add test cases

* Add utils testcases

* Exclude deleted posts

* Add doc for func

* Move api from cloud to usage

* Allow api access to authenticated users

* Change int to int64

* Fix lint issue

* Simplify err check

Co-authored-by: Ashish Bhate <ashish.bhate@mattermost.com>

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Ashish Bhate <ashish.bhate@mattermost.com>

api4/cloud_test.go

@@ -9,11 +9,11 @@ import (
 	"os"
 	"testing"
 
+	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
 
 	"github.com/mattermost/mattermost-server/v6/einterfaces/mocks"
 	"github.com/mattermost/mattermost-server/v6/model"
-	"github.com/mattermost/mattermost-server/v6/plugin/plugintest/mock"
 )
 
 func Test_getCloudLimits(t *testing.T) {