Migrate to stateless app.App (#17542)

* add request context

* move initialialization to server

* use app interface instead of global app functions

* remove app context from webconn

* cleanup

* remove duplicated services

* move context to separate package

* remove finalize init method and move content to NewServer function

* restart workers and schedulers after adding license for tests

* reflect review comments

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

app/cloud.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"time"
 
+	"github.com/mattermost/mattermost-server/v5/app/request"
 	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/mattermost/mattermost-server/v5/shared/mlog"
 )
@@ -78,13 +79,13 @@ func (a *App) SendAdminUpgradeRequestEmail(username string, subscription *model.
 	return nil
 }
 
-func (a *App) CheckAndSendUserLimitWarningEmails() *model.AppError {
+func (a *App) CheckAndSendUserLimitWarningEmails(c *request.Context) *model.AppError {
 	if a.Srv().License() == nil || (a.Srv().License() != nil && !*a.Srv().License().Features.Cloud) {
 		// Not cloud instance, do nothing
 		return nil
 	}
 
-	subscription, err := a.Cloud().GetSubscription(a.Session().UserId)
+	subscription, err := a.Cloud().GetSubscription(c.Session().UserId)
 	if err != nil {
 		return model.NewAppError(
 			"app.CheckAndSendUserLimitWarningEmails",