Monorepo migration notes - Mattermost

If you are transitioning from the non-monorepo mattermost-server to the monorepo, the easiest way to do so is to move the old mattermost server folder to something like mattermost-server-old then re-clone mattermost-server. Then:

Copy over your old config

cd server
cp ../../mattermost-server-old/config/config.json ./config/

Copy over your developer config override

cd server
cp ../../mattermost-server-old/config.override.mk ./

Update your development Docker containers for the new location of the server folder:
sh
```
cd server
make update-docker
```