* updated go mod and sum files
* fixed var-naming errors in channels/app and channels/api4 dir
* Revert "updated go mod and sum files"
This reverts commit 088dd00a848c2c31952c29f0a2a28a9fb47fc3f7.
* renamed a cost .
It was a good decision in hindsight to keep the public module as 0.x
because this would have been a breaking change again.
https://mattermost.atlassian.net/browse/MM-53032
```release-note
Changed the Go module path from github.com/mattermost/mattermost-server/server/v8 to github.com/mattermost/mattermost/server/v8.
For the public facing module, it's path is also changed from github.com/mattermost/mattermost-server/server/public to github.com/mattermost/mattermost/server/public
```
