Use flags for create post (#28857)

* Use flags for create post

* Remove unintended file

* Fix unintended change and types

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/post_persistent_notification_test.go

@@ -213,7 +213,7 @@ func TestSendPersistentNotifications(t *testing.T) {
 			},
 		},
 	}
-	_, appErr := th.App.CreatePost(th.Context, p1, th.BasicChannel, false, false)
+	_, appErr := th.App.CreatePost(th.Context, p1, th.BasicChannel, model.CreatePostFlags{})
 	require.Nil(t, appErr)
 
 	err := th.App.SendPersistentNotifications()